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

README.md

@@ -66,7 +66,10 @@ flowchart TD
 - **Media Playback Tracking** — Song title, artist, playback percentage, and cover art via Windows GSMTC
 - **Audio Mixer Control** — Real-time volume and mute from Windows default output or Voicemeeter per-strip gains, mutes, and track states
 - **Hardware Telemetry** — CPU/GPU core temps, VRAM usage from HWiNFO64
+- **Hardware Fallbacks** — Startup check reports which subsystems are available/unavailable
 - **Custom Notifications** — External scripts can push progress bars or rich text alerts via `POST /api/v1/notify`
+- **Settings Screen** — Change PIN and API token via the web client (protected by API token)
+- **Configuration Files** — Use `config.yaml`, `.env`, or environment variables
 - **E-Ink Optimized UI** — High-contrast styling, discrete zone gestures, minimal refresh
 - **System Tray .exe** — Runs unobtrusively in the Windows notification bar with a quit option
 
@@ -84,12 +87,14 @@ e-ink-dash/
 │   └── paperdash_architecture_document.txt
 ├── server/                # Python FastAPI server
 │   ├── main.py            # Application entry point
+│   ├── config.py          # Configuration management (YAML/.env/env vars)
 │   ├── audio_mixer.py     # Audio mixer abstraction (Windows + Voicemeeter)
 │   ├── media.py           # Media playback tracking (GSMTC)
 │   ├── notifications.py   # Notification system (progress + alerts)
 │   ├── telemetry.py       # Hardware telemetry (HWiNFO)
 │   ├── tray_wrapper.py    # System tray .exe wrapper
 │   ├── build_exe.py       # PyInstaller build script
+│   ├── .env.example       # Example environment file
 │   ├── requirements.txt
 │   └── tests/             # Test suite
 ├── client/                # E-Ink web client
@@ -113,10 +118,27 @@ pip install -r requirements.txt
 python -m uvicorn main:app --host 0.0.0.0 --port 8921
 ```
 
-Set environment variables:
+Configure via one of:
 
-- `DASHBOARD_PIN` — 4-digit PIN for the E-Ink client
-- `API_TOKEN` — Bearer token for external scripts
+1. **Environment variables:**
+   - `DASHBOARD_PIN` — 4-digit PIN for the E-Ink client
+   - `API_TOKEN` — Bearer token for external scripts
+
+2. **`.env` file** (in project root or exe directory):
+
+   ```
+   DASHBOARD_PIN=1234
+   API_TOKEN=your-token-here
+   ```
+
+3. **`config.yaml`** (in project root or exe directory):
+
+   ```yaml
+   dashboard_pin: "1234"
+   api_token: "your-token-here"
+   ```
+
+See `.env.example` and `config.yaml.example` for reference.
 
 ### Build .exe
 
@@ -144,6 +166,40 @@ adb install app/build/outputs/apk/debug/app-debug.apk
 
 The WebView loads `file:///android_asset/index.html` and connects to the server via WebSocket at `ws://<pc-ip>:8921/ws`.
 
+#### Localization
+
+The app supports multiple languages via Android string resources. The web client loads strings from Android via a JavaScript interface.
+
+**Adding a new language:**
+
+1. Create a new values folder: `android/app/src/main/res/values-{lang}/`
+   - Example: `values-es/` for Spanish, `values-fr/` for French
+2. Copy `values/strings.xml` to the new folder
+3. Translate the string values
+
+**Example `values-es/strings.xml`:**
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">PaperDash</string>
+    <string name="login_title">PaperDash</string>
+    <string name="login_subtitle">Ingrese PIN para conectar</string>
+    <string name="login_placeholder">****</string>
+    <string name="login_button">Conectar</string>
+    <string name="login_error_enter_pin">Ingrese un PIN</string>
+    <string name="login_error_disconnected">Desconectado. Reingrese PIN.</string>
+    <string name="connecting">Conectando…</string>
+    <string name="no_playback">Sin reproducción</string>
+    <string name="mute">SILENCIAR</string>
+    <string name="muted">SILENCIADO</string>
+    <string name="no_notifications">Sin notificaciones</string>
+    <string name="eta_prefix">ETA:</string>
+</resources>
+```
+
+The app automatically uses the device's language. No code changes needed.
+
 ### Design Decisions
 
 See `.pi/docs/design/` for detailed design decision records covering architecture, audio mixer, notifications, and the .exe build.