Prep v1.1.0 release: version string, gitignore secrets, docs

- Add VERSION = "1.1.0" to server.py; print at startup, expose via public
  GET /api/config, and show it in the admin header (so deployed == released
  is verifiable at a glance).
- Ignore config.json in .gitignore — it holds the admin password hash and
  session secret; fresh installs use config.json.example.
- README/CLAUDE.md: document the in-app pixel editor (now with shape tools,
  select/move, reference overlay, custom/recent palettes), the receiver health
  dashboard, 9 sprite types, and the asset cache-busting convention.
- Bump admin asset cache-bust to ?v=20260609d.

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

.gitignore

@@ -23,5 +23,6 @@ __pycache__/
 .DS_Store
 Thumbs.db
 
-# Local config (uncomment if you want to ignore local changes)
-# config.json
+# Local config — contains the admin password hash and session secret.
+# Fresh installs start from config.json.example (see CONFIG.md).
+config.json