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>

.github/workflows/release.yml

@@ -7,6 +7,12 @@ name: Release
 on:
   push:
     tags: ["v*"]
+  workflow_dispatch:
+    inputs:
+      version:
+        description: "Image tag to publish (e.g. 1.1.2); leave blank for just :latest"
+        required: false
+        default: ""
 
 permissions:
   contents: read
@@ -40,6 +46,7 @@ jobs:
           tags: |
             type=semver,pattern={{version}}
             type=semver,pattern={{major}}.{{minor}}
+            type=raw,value=${{ inputs.version }},enable=${{ github.event_name == 'workflow_dispatch' && inputs.version != '' }}
             type=raw,value=latest
 
       - name: Build and push