Add production deployment tooling: Nginx, Gitea, prod Dockerfiles

Sets up everything needed to deploy behind Cloudflare with a self-hosted
git server: multi-stage prod Dockerfiles (non-root), docker-compose.prod.yml
(Postgres/Redis with no host ports, Nginx reverse proxy, Gitea with
public-read/admin-write access control), scripts/bootstrap-env.sh to
auto-generate required secrets on first clone, and DEPLOYMENT.md covering
the full runbook. Provider API keys (Anthropic/Brave/NinjaPear/USPTO/
Turnstile) are deliberately kept out of .env in favor of the existing
DB-backed Settings UI, so the public repo stays safe to expose.

Also fixes two bugs only surfaced by live-testing the prod stack: Celery
beat couldn't write its schedule file as a non-root user, and Gitea's
embedded SSH server conflicted with the base image's own sshd on port 22.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

.gitignore

@@ -16,8 +16,12 @@ venv/
 htmlcov/
 .coverage
 *.db
+*.db-journal
+*.db-shm
+*.db-wal
 *.sqlite3
 .fixture_state
+celerybeat-schedule
 
 # --- Node / Next.js ---
 node_modules/