feat: config files, settings screen, hardware check

- Add config.py with multi-source config (YAML, .env, env vars)
- Add .env.example and config.yaml.example
- Add settings API endpoints (GET/POST /api/v1/settings)
- Add status endpoint (GET /api/v1/status) with hardware subsystem check
- Add settings screen to web client (protected by API token)
- Add localization strings for settings UI
- Add tests for config module and new endpoints
- Update README with config documentation

config.yaml.example

@@ -0,0 +1,9 @@
+# PaperDash Configuration
+# Copy this file to config.yaml and fill in your values
+
+dashboard_pin: "1234"
+api_token: "your-secret-token-here"
+
+host: "0.0.0.0"
+port: 8921
+log_level: INFO