feat(workspace): journal with one note per day and a calendar

- journal_days (migration 8) maps a person's day to an ordinary note;
  GET /journal lists the days, POST /journal/{date} opens or creates one
- the journal sits on top of the notes sidebar: days below each other
  (today first, older ones load while scrolling), a calendar with month
  and year picker follows the day in view and jumps to any day
- the header shares the day in view; journal notes stay out of the folder
  tree; can be switched off per device under Darstellung

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/workspace/JournalView.tsx

@@ -0,0 +1,246 @@
+import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { ArrowLeft, CalendarDays, ChevronDown, Users } from 'lucide-react';
+import { Document, JournalDay, User } from '../../lib/types';
+import { shortDateLabel, todayISO } from '../../lib/journal';
+import { DocumentEditor } from './DocumentEditor';
+import { JournalCalendar } from './JournalCalendar';
+
+const PAGE = 7;
+
+interface JournalViewProps {
+  days: JournalDay[];
+  /** Days jumped to over the calendar (shown even while still empty) */
+  extraDates: string[];
+  activeDate: string;
+  onActiveDateChange: (date: string) => void;
+  /** Set by the calendar; the view scrolls there (nonce: the same day again) */
+  jumpRequest: { date: string; nonce: number } | null;
+  /** Opens (creates on first use) the note of a day */
+  onOpenDay: (date: string) => Promise<Document | null>;
+  onJump: (date: string) => void;
+  getDoc: (id: string) => Document | undefined;
+  currentUser?: User | null;
+  availableFolders: string[];
+  onOpenShareModal: (doc: Document) => void;
+  onDocMetadataChange: (updated: Document) => void;
+  onDeleteDoc: (docId: string) => void;
+  onSelectTag: (tag: string) => void;
+  onWikiLinkClick?: (pageTitle: string) => void;
+  onOpenDocBlock?: (docId: string, blockId?: string) => void;
+  onOpenTask?: (taskId: string) => void;
+  onBackMobile: () => void;
+  /** A day was saved (its calendar dot may change) */
+  onDaySaved: () => void;
+}
+
+// The journal: one note per day below each other, today on top, older days load while scrolling.
+export const JournalView: React.FC<JournalViewProps> = ({
+  days,
+  extraDates,
+  activeDate,
+  onActiveDateChange,
+  jumpRequest,
+  onOpenDay,
+  onJump,
+  getDoc,
+  currentUser,
+  availableFolders,
+  onOpenShareModal,
+  onDocMetadataChange,
+  onDeleteDoc,
+  onSelectTag,
+  onWikiLinkClick,
+  onOpenDocBlock,
+  onOpenTask,
+  onBackMobile,
+  onDaySaved,
+}) => {
+  const today = todayISO();
+  const docIdByDate = useMemo(() => new Map(days.map((d) => [d.date, d.docId])), [days]);
+  const entryDates = useMemo(() => new Set(days.filter((d) => !d.empty).map((d) => d.date)), [days]);
+
+  // Today, every day with text and the days jumped to – newest first
+  const dates = useMemo(() => {
+    const set = new Set<string>([today, ...extraDates]);
+    days.forEach((d) => {
+      if (!d.empty) set.add(d.date);
+    });
+    return Array.from(set).sort((a, b) => b.localeCompare(a));
+  }, [days, extraDates, today]);
+
+  const [limit, setLimit] = useState(PAGE);
+  const shown = dates.slice(0, limit);
+  const [showCalendar, setShowCalendar] = useState(false);
+
+  // Days on screen without a note yet (today, a day jumped to) get one
+  const opening = useRef(new Set<string>());
+  useEffect(() => {
+    shown.forEach((date) => {
+      if (!docIdByDate.has(date) && !opening.current.has(date)) {
+        opening.current.add(date);
+        void onOpenDay(date).finally(() => opening.current.delete(date));
+      }
+    });
+  }, [shown, docIdByDate, onOpenDay]);
+
+  const scrollRef = useRef<HTMLDivElement | null>(null);
+  const sectionRefs = useRef(new Map<string, HTMLElement>());
+
+  // Jump: make sure the day is rendered, then scroll to it once its note is there
+  const pendingJump = useRef<string | null>(null);
+  const handledJump = useRef(0);
+  useEffect(() => {
+    if (!jumpRequest || handledJump.current === jumpRequest.nonce) return;
+    const idx = dates.indexOf(jumpRequest.date);
+    if (idx === -1) return; // the parent adds the day first
+    handledJump.current = jumpRequest.nonce;
+    if (idx >= limit) setLimit(idx + PAGE);
+    pendingJump.current = jumpRequest.date;
+  }, [jumpRequest, dates, limit]);
+  useEffect(() => {
+    const date = pendingJump.current;
+    if (!date) return;
+    const el = sectionRefs.current.get(date);
+    if (el && docIdByDate.has(date)) {
+      pendingJump.current = null;
+      el.scrollIntoView({ block: 'start' });
+    }
+  });
+
+  // The day at the top of the scroll area is the active one (calendar, share button)
+  const onScroll = useCallback(() => {
+    const root = scrollRef.current;
+    if (!root) return;
+    const top = root.getBoundingClientRect().top + 48;
+    let current = shown[0];
+    for (const date of shown) {
+      const el = sectionRefs.current.get(date);
+      if (!el) continue;
+      if (el.getBoundingClientRect().top <= top) current = date;
+      else break;
+    }
+    if (current && current !== activeDate) onActiveDateChange(current);
+  }, [shown, activeDate, onActiveDateChange]);
+
+  // Load older days when the end comes into view
+  const sentinelRef = useRef<HTMLDivElement | null>(null);
+  useEffect(() => {
+    const el = sentinelRef.current;
+    const root = scrollRef.current;
+    if (!el || !root || typeof IntersectionObserver === 'undefined' || limit >= dates.length) return;
+    const observer = new IntersectionObserver(
+      ([entry]) => {
+        if (entry.isIntersecting) setLimit((l) => l + PAGE);
+      },
+      { root, rootMargin: '400px 0px' }
+    );
+    observer.observe(el);
+    return () => observer.disconnect();
+  }, [limit, dates.length]);
+
+  const activeDocId = docIdByDate.get(activeDate);
+  const activeDoc = activeDocId ? getDoc(activeDocId) : undefined;
+  const sharedCount = activeDoc?.sharedWith?.length ?? 0;
+
+  return (
+    <div className="flex-1 flex flex-col min-h-0 bg-editor">
+      {/* One header for all days: the day in view and its sharing */}
+      <div className="shrink-0 flex items-center gap-2 px-4 sm:px-6 py-2 border-b border-border">
+        <button
+          type="button"
+          onClick={onBackMobile}
+          className="lg:hidden btn-icon shrink-0 h-11 w-11"
+          title="Zurück zur Seitenleiste"
+        >
+          <ArrowLeft className="w-3.5 h-3.5" />
+        </button>
+        <button
+          type="button"
+          onClick={() => setShowCalendar((v) => !v)}
+          className="lg:pointer-events-none flex-1 min-w-0 flex items-center gap-1.5 text-xs text-main font-medium text-left cursor-pointer"
+          aria-expanded={showCalendar}
+          title="Kalender"
+        >
+          <CalendarDays className="w-3.5 h-3.5 text-accent shrink-0" />
+          <span className="truncate">Journal · {shortDateLabel(activeDate)}</span>
+          <ChevronDown className={`lg:hidden w-3.5 h-3.5 text-muted shrink-0 transition-transform ${showCalendar ? 'rotate-180' : ''}`} />
+        </button>
+        {activeDate !== today && (
+          <button
+            type="button"
+            onClick={() => onJump(today)}
+            className="btn-action shrink-0 h-11 sm:h-7 px-2.5 text-xs"
+          >
+            Heute
+          </button>
+        )}
+        <button
+          type="button"
+          disabled={!activeDoc || !activeDoc.isOwner}
+          onClick={() => activeDoc && onOpenShareModal(activeDoc)}
+          className="btn-icon shrink-0 h-11 w-11 sm:h-7 sm:w-auto sm:px-2 gap-1 disabled:opacity-40"
+          title={activeDoc ? `${activeDoc.title} teilen` : 'Teilen'}
+        >
+          <Users className="w-3.5 h-3.5" />
+          <span className="hidden sm:inline text-xs">{sharedCount > 0 ? `Geteilt (${sharedCount})` : 'Teilen'}</span>
+        </button>
+      </div>
+
+      {showCalendar && (
+        <div className="lg:hidden shrink-0 px-4 py-3 border-b border-border bg-sidebar">
+          <JournalCalendar
+            activeDate={activeDate}
+            entryDates={entryDates}
+            onSelect={(date) => {
+              setShowCalendar(false);
+              onJump(date);
+            }}
+          />
+        </div>
+      )}
+
+      <div ref={scrollRef} onScroll={onScroll} className="flex-1 min-h-0 overflow-y-auto">
+        {shown.map((date) => {
+          const docId = docIdByDate.get(date);
+          return (
+            <section
+              key={date}
+              data-journal-date={date}
+              ref={(el) => {
+                if (el) sectionRefs.current.set(date, el);
+                else sectionRefs.current.delete(date);
+              }}
+              className="border-b border-border last:border-b-0 min-h-[8rem]"
+            >
+              {docId ? (
+                <DocumentEditor
+                  key={docId}
+                  variant="journal"
+                  docId={docId}
+                  currentUser={currentUser}
+                  initialDoc={getDoc(docId) || null}
+                  availableFolders={availableFolders}
+                  onDocMetadataChange={onDocMetadataChange}
+                  onDeleteDoc={onDeleteDoc}
+                  onOpenShareModal={onOpenShareModal}
+                  onSelectTag={onSelectTag}
+                  onWikiLinkClick={onWikiLinkClick}
+                  onOpenDocBlock={onOpenDocBlock}
+                  onOpenTask={onOpenTask}
+                  onSaveStatusChange={(status) => {
+                    if (status === 'saved') onDaySaved();
+                  }}
+                />
+              ) : (
+                <div className="px-4 sm:px-8 py-6 text-xs text-muted">{shortDateLabel(date)} wird geöffnet…</div>
+              )}
+            </section>
+          );
+        })}
+        {limit < dates.length && <div ref={sentinelRef} className="h-12" />}
+        {/* Room below the oldest day, so every day can be scrolled to the top */}
+        <div className="h-[60vh]" aria-hidden />
+      </div>
+    </div>
+  );
+};