feat(E): Unified Search — 24 Tasks complete

- SPIKE-E: FTS+Vector+Permission benchmark on 10k records (all <30ms)
- E-PROV: supports_fts/vector/rag/graph capability flags on all providers
- E-FTS/VEC: All 11 providers refactored to BaseSearchProvider with permission filtering
- E-PERM: Over-fetch strategy for vector+permission (15x faster than ANY() filter)
- E-FUSE: rrf_fusion_multi() for N-way RRF over FTS+Vector+RAG+Graph
- E-LLM: Query understanding cleaned up to use central llm_complete()
- E-CHUNK: Document chunking module + document_chunks table with HNSW index
- E-EMB: Chunk embedding ARQ jobs (index_file_chunks, reindex_chunks)
- E-RAG: RAG retrieval via FileSearchProvider.search_rag()
- E-GRAPH: GraphRAG BFS traversal via GraphRAGSearchProvider.search_graph()
- E-IX-EVT: Auto-indexing via outbox events + delete/cleanup handlers
- E-IX-RE: Batch reindex with progress tracking + reindex_all job
- E-DATA-LIFE: Lifecycle module (remove/rebuild/restore/correct) + API endpoints
- E-K-MEM: AgentMemorySearchProvider
- E-P-AI: AIChatSearchProvider
- E-P-WF: WorkflowSearchProvider
- E-P-COMM: ConversationSearchProvider verified (already on BaseSearchProvider)
- E-API: Filter params (date_from/to, tags, sort) + /facets endpoint
- E-TOOL: unified_search AI tool registered in ToolRegistry
- E-MCP: Search tool in MCP server with normal RBAC/tenant checks
- E-UI-CMD: CommandPalette (Cmd+K) with debounced search + recent searches
- E-UI-FAC: SearchFacets, SearchResultCard, SavedSearches components
- E-TEST: 40 new tests in test_unified_search_phase_e.py (105 total green)
- E-DOC: api-documentation.md, plugin-development-guide.md, test-strategy.md updated

105 tests passing, TypeScript clean.

frontend/src/i18n/locales/de.json

@@ -329,7 +329,18 @@
     "enterQuery": "Geben Sie einen Suchbegriff ein.",
     "mails": "E-Mails",
     "files": "Dateien",
-    "events": "Termine"
+    "events": "Termine",
+    "messages": "Nachrichten",
+    "tags": "Tags",
+    "dateRange": "Zeitraum",
+    "sortRelevance": "Relevanz",
+    "sortDate": "Datum",
+    "sortName": "Name",
+    "score": "Relevanz-Score",
+    "savedSearches": "Gespeicherte Suchen",
+    "saveSearch": "Suche speichern",
+    "saveSearchName": "Name der Suche",
+    "noSavedSearches": "Noch keine gespeicherten Suchen."
   },
   "topbar": {
     "tenant": "Mandant",
@@ -339,7 +350,18 @@
     "userMenu": "Benutzermenü",
     "profile": "Profil",
     "settings": "Einstellungen",
-    "logout": "Abmelden"
+    "logout": "Abmelden",
+    "commandPalette": "Befehlspalette öffnen",
+    "commandPaletteHint": "Befehlspalette (Strg+K)"
+  },
+  "commandPalette": {
+    "title": "Globale Suche",
+    "placeholder": "Suchen... (Strg+K)",
+    "results": "Suchergebnisse",
+    "recent": "Letzte Suchen",
+    "hint": "Geben Sie einen Suchbegriff ein oder drücken Sie Strg+K.",
+    "noResults": "Keine Ergebnisse für \"{{query}}\" gefunden.",
+    "error": "Suche fehlgeschlagen. Bitte versuchen Sie es erneut."
   },
   "toast": {
     "success": "Erfolg",

frontend/src/i18n/locales/en.json

@@ -329,7 +329,18 @@
     "enterQuery": "Enter a search term.",
     "mails": "Emails",
     "files": "Files",
-    "events": "Events"
+    "events": "Events",
+    "messages": "Messages",
+    "tags": "Tags",
+    "dateRange": "Date Range",
+    "sortRelevance": "Relevance",
+    "sortDate": "Date",
+    "sortName": "Name",
+    "score": "Relevance Score",
+    "savedSearches": "Saved Searches",
+    "saveSearch": "Save Search",
+    "saveSearchName": "Search name",
+    "noSavedSearches": "No saved searches yet."
   },
   "topbar": {
     "tenant": "Tenant",
@@ -339,7 +350,18 @@
     "userMenu": "User Menu",
     "profile": "Profile",
     "settings": "Settings",
-    "logout": "Sign Out"
+    "logout": "Sign Out",
+    "commandPalette": "Open command palette",
+    "commandPaletteHint": "Command palette (Ctrl+K)"
+  },
+  "commandPalette": {
+    "title": "Global Search",
+    "placeholder": "Search... (Ctrl+K)",
+    "results": "Search results",
+    "recent": "Recent searches",
+    "hint": "Type a search term or press Ctrl+K.",
+    "noResults": "No results found for \"{{query}}\".",
+    "error": "Search failed. Please try again."
   },
   "toast": {
     "success": "Success",