chore: bootstrap repository with governance docs

Initialize git, add Apache-2.0 LICENSE, .gitattributes (LF line
endings), AGENTS.md (entry points, stack, discovery order, baseline
checks), RUNBOOK.md (dev boot, prod deploy with overlay, ingestion,
failures, rollback, scaling notes), .env.prod.example with rotated
credential placeholders, and dev-only warnings on .env.example.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/workers/celery_app.py

@@ -0,0 +1,28 @@
+"""Celery application instance."""
+
+from __future__ import annotations
+
+from celery import Celery
+
+from app.config import settings
+from app.logging_config import configure_logging
+
+configure_logging()
+
+celery_app = Celery(
+    "legacyhub",
+    broker=settings.redis_url,
+    backend=settings.redis_url,
+    include=["app.workers.tasks"],
+)
+
+celery_app.conf.update(
+    task_acks_late=True,
+    task_reject_on_worker_lost=True,
+    task_track_started=True,
+    worker_prefetch_multiplier=1,
+    task_time_limit=settings.max_document_timeout_seconds * 4,
+    task_soft_time_limit=settings.max_document_timeout_seconds * 3,
+    timezone="UTC",
+    enable_utc=True,
+)

app/workers/tasks.py

@@ -0,0 +1,22 @@
+"""Celery tasks - thin wrappers over pipeline functions."""
+
+from __future__ import annotations
+
+import uuid
+
+from celery.utils.log import get_task_logger
+
+from app.workers.celery_app import celery_app
+
+logger = get_task_logger(__name__)
+
+
+@celery_app.task(name="legacyhub.process_document", bind=True, max_retries=2, default_retry_delay=30)
+def process_document(self, document_id: str, run_id: str | None = None) -> dict:
+    from app.ingestion.pipeline import process_document_id
+
+    try:
+        return process_document_id(uuid.UUID(document_id), uuid.UUID(run_id) if run_id else None)
+    except Exception as exc:  # noqa: BLE001
+        logger.exception("worker.process_failed", extra={"document_id": document_id})
+        raise self.retry(exc=exc) from exc