Add workspaces, computers, bot memory and the bots queue

- Schema: workspaces (+ workspace_bots, workspace_computers), containers,
  computers, bot_computers, bots.memory, workspaces.system_prompt, and
  bots_queue as a bun-sqlite isQueue table
- Main computer (and its container record) ensured with the coordinator on
  signup, seed and /admin/bots; the coordinator's access to it is locked
- Effective computer access: direct grants plus workspace computers
- Full bot prompt: core instructions, workspace prompts, then memory;
  bots can rewrite their memory and system prompt
- Queue helpers on the native BunSQLite.queue API, plus a handler that
  heartbeats, serializes per computer, recovers after restarts, reports
  lost jobs, supports cancelling and pushes outcomes over the WebSocket
- Enable SQLite foreign keys at startup so schema cascades fire
- Prune finished jobs daily

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

src/dict/bot-queue-dict.ts

@@ -0,0 +1,11 @@
+/**
+ * `last_error` of a job the user cancelled. Cancelled jobs are `failed`
+ * (bun-sqlite queues have no cancelled status) with this error.
+ */
+export const BotJobCancelledError = "Cancelled";
+
+/**
+ * `last_error` bun-sqlite sets when it releases a job whose handler went
+ * silent past the lock timeout on its last attempt.
+ */
+export const BotJobLockTimedOutError = "Lock timed out";