feat(mobile): add context-sensitive MindSift logo menu, slide-over file drawer, and larger touch targets

frontend/src/context/MobileActionContext.tsx

@@ -0,0 +1,62 @@
+import React, { createContext, useContext, useState, useCallback } from 'react';
+
+export interface MobileActionItem {
+  id: string;
+  label: string;
+  icon?: React.ReactNode;
+  badge?: string | number;
+  variant?: 'default' | 'accent' | 'danger';
+  active?: boolean;
+  onClick: () => void;
+}
+
+export interface MobileMenuGroup {
+  id: string;
+  title?: string;
+  items: MobileActionItem[];
+}
+
+interface MobileActionContextValue {
+  groups: MobileMenuGroup[];
+  setGroups: (groups: MobileMenuGroup[]) => void;
+  isMenuOpen: boolean;
+  setIsMenuOpen: React.Dispatch<React.SetStateAction<boolean>>;
+  closeMenu: () => void;
+}
+
+const MobileActionContext = createContext<MobileActionContextValue>({
+  groups: [],
+  setGroups: () => {},
+  isMenuOpen: false,
+  setIsMenuOpen: () => {},
+  closeMenu: () => {},
+});
+
+export const MobileActionProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
+  const [groups, setGroupsState] = useState<MobileMenuGroup[]>([]);
+  const [isMenuOpen, setIsMenuOpen] = useState(false);
+
+  const setGroups = useCallback((newGroups: MobileMenuGroup[]) => {
+    setGroupsState(newGroups);
+  }, []);
+
+  const closeMenu = useCallback(() => {
+    setIsMenuOpen(false);
+  }, []);
+
+  return (
+    <MobileActionContext.Provider
+      value={{
+        groups,
+        setGroups,
+        isMenuOpen,
+        setIsMenuOpen,
+        closeMenu,
+      }}
+    >
+      {children}
+    </MobileActionContext.Provider>
+  );
+};
+
+export const useMobileActions = () => useContext(MobileActionContext);