feat: add ARQ background worker to container

- Create app/core/worker.py with WorkerSettings for ARQ
- Register all job functions: reindex, index_*, embedding_batch, deep_analysis
- Update prestart.sh to start ARQ worker in background before uvicorn
- Worker runs with max_jobs=10, job_timeout=300s

app/core/worker.py

@@ -0,0 +1,88 @@
+"""ARQ worker configuration and entrypoint."""
+
+from __future__ import annotations
+
+import logging
+from typing import Any
+
+from arq.connections import RedisSettings
+
+from app.config import get_settings
+
+logger = logging.getLogger(__name__)
+
+
+def _get_redis_settings() -> RedisSettings:
+    """Get Redis settings from app config."""
+    settings = get_settings()
+    return RedisSettings.from_dsn(settings.redis_url)
+
+
+async def on_startup(ctx: dict[str, Any]) -> None:
+    """Called when worker starts."""
+    logger.info("ARQ worker starting...")
+
+
+async def on_shutdown(ctx: dict[str, Any]) -> None:
+    """Called when worker shuts down."""
+    logger.info("ARQ worker shutting down...")
+
+
+def _collect_job_functions() -> dict[str, Any]:
+    """Collect all job functions from plugins and core.
+
+    Each plugin's jobs module may define async functions with the
+    signature (ctx: dict, *args) -> None. We import them all and
+    register by name.
+    """
+    functions: dict[str, Any] = {}
+
+    # Unified search jobs
+    try:
+        from app.plugins.builtins.unified_search.jobs import (
+            index_mails,
+            index_file,
+            index_contact,
+            index_company,
+            index_event,
+            reindex,
+            embedding_batch,
+        )
+        functions.update({
+            "index_mails": index_mails,
+            "index_file": index_file,
+            "index_contact": index_contact,
+            "index_company": index_company,
+            "index_event": index_event,
+            "reindex": reindex,
+            "embedding_batch": embedding_batch,
+        })
+    except Exception:
+        logger.warning("Failed to import unified_search jobs", exc_info=True)
+
+    # AI proactive jobs
+    try:
+        from app.plugins.builtins.ai_proactive.jobs import deep_analysis
+        functions["deep_analysis"] = deep_analysis
+    except Exception:
+        logger.warning("Failed to import ai_proactive jobs", exc_info=True)
+
+    # Calendar jobs (calendar_reminder is enqueued but no handler exists yet)
+    # try:
+    #     from app.plugins.builtins.calendar.jobs import calendar_reminder
+    #     functions["calendar_reminder"] = calendar_reminder
+    # except Exception:
+    #     logger.warning("Failed to import calendar jobs", exc_info=True)
+
+    return functions
+
+
+class WorkerSettings:
+    """ARQ worker settings."""
+    functions = _collect_job_functions()
+    redis_settings = _get_redis_settings()
+    on_startup = on_startup
+    on_shutdown = on_shutdown
+    max_jobs = 10
+    job_timeout = 300
+    queue_name = "arq:queue"