feat(coord): DB migration — project-scoped missions, multi-tenant RBAC

Closes #131

- Add userId, phase, milestones, config columns to missions table
- Add new mission_tasks table for coord-managed task tracking
- Both tables enforce per-user RBAC via userId foreign key
- Generate Drizzle migration (0001_magical_rattler.sql)
- Add userId-scoped query methods to brain missions repo
- Add new mission-tasks repo to brain package
- Extend CoordService with DB-backed mission and task CRUD
- Extend CoordController with DB-backed REST endpoints
- Preserve file-based coord endpoints for backwards compatibility

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/db/drizzle/meta/_journal.json

@@ -8,6 +8,13 @@
       "when": 1773368153122,
       "tag": "0000_loud_ezekiel_stane",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "7",
+      "when": 1773602195609,
+      "tag": "0001_magical_rattler",
+      "breakpoints": true
     }
   ]
-}
+}