Release v1.1.2: publish container image + add security workflows

- Bump VERSION to 1.1.2 (no app behavior change from 1.1.1).
- release.yml: add workflow_dispatch so images can be published manually from
  the Actions tab in addition to on version tags.
- Add CodeQL code scanning (Python + JavaScript), free for public repos.
- Add Dependabot config for GitHub Actions and pip updates.

This is the first release to publish a multi-arch image to GHCR
(ghcr.io/allennpit/ads-bit).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server.py

@@ -17,7 +17,7 @@ from aiohttp import web, ClientSession, ClientTimeout
 import netifaces
 import bcrypt
 
-VERSION = "1.1.1"
+VERSION = "1.1.2"
 
 WEB_DIR = Path(__file__).parent
 # Config path is overridable (handy for containers persisting config on a