revamp analytics & logs — per-agent attribution, unified log timeline

- Move analytics endpoints to Postgres with agent filtering that matches both stamps (api_key for external traffic, agent_id for owner/headless)
- Add tool & schedule analytics, token grouping (model/agent/source) and side-channel toggle
- Merge chat/system/webhook/workflow/schedule events into one logs timeline with level/type/search filters
- Stamp user/agent on tool_call_attempts at propose time (migration 0018) and backfill via parent message
- Frontend: revamped Analytics charts and Logs page

tests/e2e/specs/tier-a/user-logs.spec.ts

@@ -47,7 +47,6 @@ interface GetLogsResponse {
     user: string | null;
     question: string | null;
     sources: unknown;
-    retriever_params: unknown;
     timestamp: string | null;
   }>;
   page: number;