feat: Operational hardening — healthcheck, config refactor, requirements lock

- Add GET /health route (DB + Redis ping, 200/503) with Dockerfile HEALTHCHECK directive
- Replace config.py stub with real pydantic BaseSettings reading directly from env vars;
  remove external config file mount from docker-compose
- Add requirements.lock (pip freeze snapshot for bit-identical builds)
- Untrack config.py globally but allow app/config.py via .gitignore negation

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

app/routers/registry.py

@@ -1,7 +1,7 @@
 from fastapi import FastAPI, Depends
 from app.routers.dependencies_v3 import DeprecationParams
 from app.routers import (
-    ae_obj, aether_cfg, api_crud, api_crud_v2, api_crud_v3, api, importing, sql,
+    ae_obj, aether_cfg, api_crud, api_crud_v2, api_crud_v3, api, health, importing, sql,
     account, contact, data_store,
     event, event_badge, event_badge_importing, event_badge_template,
     event_device, event_exhibit, event_exhibit_tracking, event_file, event_importing,
@@ -17,6 +17,7 @@ def setup_routers(app: FastAPI):
     """
     Registers all application routers with their respective prefixes and tags.
     """
+    app.include_router(health.router, tags=['Root'])
     app.include_router(ae_obj.router, prefix='/ae_obj', tags=['AE Object'])
     app.include_router(aether_cfg.router, tags=['Aether Config'])
     # app.include_router(api_crud.router, prefix='/crud', tags=['CRUD v1.2 (Legacy)'], dependencies=[Depends(DeprecationParams)])