feat(ai-chat): per-user AI agent backend — LLM config, read-only agent, provenance schema

WIP checkpoint of the gitmost AI-chat backend (plan stages A + B1 + B3a).
The agent acts under the requesting user's JWT (Docmost CASL enforces page
access); the external service-account /mcp endpoint is untouched.

LLM provider config (A2-A4):
- integrations/crypto: AES-256-GCM SecretBoxService (key derived from APP_SECRET,
  per-record salt/iv; clear error on rotation instead of crashing).
- ai_provider_credentials table/repo/types: encrypted API key stored outside
  workspace settings/baseFields, write-only (never returned by any endpoint).
- integrations/ai: per-workspace AI SDK v6 provider driver (openai/gemini/ollama),
  admin-gated GET(masked)/PATCH(write-only key)/Test endpoints; settings.ai.provider
  holds non-secret config incl. systemPrompt. Removed unused AI_* env getters (DB is
  the single source of truth).

Chat module (A1, A5-A8):
- ai_chats/ai_chat_messages repos (workspace-scoped, soft-delete, tsv never selected).
- core/ai-chat: CRUD + POST /ai-chat/stream (Fastify hijack + AI SDK v6
  pipeUIMessageStreamToResponse, abort on disconnect, persist user/assistant msgs).
- Agent loop: streamText + stepCountIs(8); read tools searchPages/getPage via a
  per-request DocmostClient over loopback REST under the user's minted access token.
- Gate settings.ai.chat (+ 503 when provider unconfigured); buildSystemPrompt with a
  non-removable safety/anti-prompt-injection framework. Per-user rate limit.

Per-user auth (B1):
- @docmost/mcp DocmostClient gains an additive getToken variant (carry a user JWT,
  re-fetch on 401) and exports DocmostClient; the email/password service-account path
  (external /mcp, stdio) is unchanged.

Agent-edit provenance backbone (B3a):
- Migration: pages/page_history (last_updated_source, last_updated_ai_chat_id) and
  comments (created_source, ai_chat_id, resolved_source).
- Signed actor/aiChatId claim in the collab token; onAuthenticate propagates it,
  onStoreDocument writes it with a sticky agent marker, saveHistory copies it.

Migrations auto-run on boot (additive). Write tools, frontend, RAG and external MCP
servers are not in this checkpoint.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/core/auth/services/token.service.ts

@@ -42,7 +42,13 @@ export class TokenService {
     return this.jwtService.sign(payload);
   }
 
-  async generateCollabToken(user: User, workspaceId: string): Promise<string> {
+  async generateCollabToken(
+    user: User,
+    workspaceId: string,
+    // Optional agent-edit provenance. When omitted (the human collab path), the
+    // token carries no actor/aiChatId and is treated as 'user' downstream.
+    provenance?: { actor: 'agent'; aiChatId: string },
+  ): Promise<string> {
     if (isUserDisabled(user)) {
       throw new ForbiddenException();
     }
@@ -51,6 +57,9 @@ export class TokenService {
       sub: user.id,
       workspaceId,
       type: JwtType.COLLAB,
+      ...(provenance
+        ? { actor: provenance.actor, aiChatId: provenance.aiChatId }
+        : {}),
     };
     const expiresIn = '24h';
     return this.jwtService.sign(payload, { expiresIn });