refactor(notes): remove legacy whole-document saves; all block changes go through sync

Phase 5 of the collaboration plan:
- Remove PATCH /documents/{id}/blocks, PatchDocumentBlocks, the
  DOC_BLOCKS_PATCHED event and its types, FlushDocumentState and
  LoadDocumentState. PUT /documents/{id} rejects blocks (400) and only
  changes title, icon, folder and pin; editors may now change title/icon.
- The to-do overview ticks via a single operation on /docs/{id}/sync
  (new skipLog flag). Task links set the block tick with a targeted
  operation and notify open editors; creating a linked task needs edit
  rights.
- Keep the three share tables: DocRole already decides centrally, and
  rewriting the visibility queries would only add risk (documented in plan).
- Tests adapted to the new paths; share e2e test now also ticks a to-do in
  the overview.

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

internal/api/docsync.go

@@ -86,6 +86,7 @@ func (s *Server) handleDocSync(w http.ResponseWriter, r *http.Request) {
 			Hold    []string `json:"hold"`
 			Release []string `json:"release"`
 		} `json:"leases"`
+		SkipLog bool `json:"skipLog"` // one-off changes (e.g. ticking a to-do in the overview) need no log
 	}
 	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, syncMaxBody)).Decode(&req); err != nil {
 		writeError(w, http.StatusBadRequest, "Ungültiges JSON")
@@ -149,12 +150,16 @@ func (s *Server) handleDocSync(w http.ResponseWriter, r *http.Request) {
 		s.afterDocChange(docID, req.Ops, resp.Results)
 	}
 
-	entries, head, err := s.store.GetDocOpsSince(docID, req.LastSeq, syncMaxLog)
+	logLimit := syncMaxLog
+	if req.SkipLog {
+		logLimit = 0
+	}
+	entries, head, err := s.store.GetDocOpsSince(docID, req.LastSeq, logLimit)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
 		return
 	}
-	if req.LastSeq > head {
+	if req.LastSeq > head && !req.SkipLog {
 		resp.Resync = true
 		entries = []storage.DocLogEntry{}
 	}