Add knowledgebases

Knowledgebases give bots RAG over documents, scoped like extensions: to
particular bots, to a workspace, or to every bot, with their own button
beside Tools in the composer. Documents are chunked and embedded by the
file-ingest worker with the install's embedding model, which is now an
install-wide setting rather than a per-bot one.

- Word search runs on an FTS5 index ranked by BM25, with a scored LIKE
  fallback for scripts written without spaces.
- Changing the embedding model re-indexes documents automatically.
- Ingest jobs wait without spending attempts while every embedding model
  rests, fail at once on errors retrying can't fix, and keep passages
  searchable by words when the model refuses.
- Settings > Knowledgebases shows each knowledgebase's and document's
  index state: spinner, warning, grey check (words only) or green check.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/dict/settings-pages-dict.ts

@@ -6,6 +6,7 @@ import {
     DatabaseBackup,
     KeyRound,
     Layers,
+    Library,
     LockKeyhole,
     Monitor,
     Plug,
@@ -61,6 +62,7 @@ export const SettingsPages: SettingsPage[] = [
     { title: "MCPs", url: "/admin/settings/mcps", Icon: Plug, can_view: canManageCrew },
     { title: "Tools", url: "/admin/settings/tools", Icon: Wrench, can_view: canManageCrew },
     { title: "Skills", url: "/admin/settings/skills", Icon: BookOpen, can_view: canManageCrew },
+    { title: "Knowledgebases", url: "/admin/settings/knowledgebases", Icon: Library, can_view: canManageCrew },
     {
         title: "Users",
         url: "/admin/settings/users",