implement: Phase 25.5 device config from JSON file

- Create config/device.json with owner_name, car_model, device_name, avatar_path
- Update app_account.py to load owner_name and avatar_path from config
- Update app_car.py to load car_model and device_name from config
- Update base.html template to use avatar_path from config instead of hardcoded
- Add graceful fallback to hardcoded defaults if config file missing
- Document in deploy/readme.md and readme.md how to customize device identity
- Update PLAN.md Phase 25.5 to reflect current implementation and future server sync

Benefits:
- No code edits needed to customize Pi (edit JSON file only)
- Offline-first: all values loaded from local file at startup
- Connection-driven sync planned for Phase 25.5a (sync when internet available, not on timer)
- Server becomes source of truth after Phase 25.5a implementation

All 63 tests passing. Database filename still based on owner_name, with migration warning in docs.

Co-authored-by: Copilot <[email protected]>

readme.md

@@ -114,33 +114,70 @@ in [deploy/](./deploy). For a clean-install walkthrough on a fresh Pi, use
 
 For the remote server (receives trip logs + dashcam uploads), see [server/README.md](./server/README.md).
 
-## Customizing username and profile picture
+## Customizing device identity
 
-The top-right username and avatar in the local app are currently code-configured.
+The Pi displays a username, car model, and avatar image. All customizable values are stored in `config/device.json` (no code edits needed).
 
-### Change username
+### Edit device configuration
 
-Edit [modules/app_account.py](./modules/app_account.py):
+Edit [config/device.json](./config/device.json):
 
-```python
-self.name = "quoije"
+```json
+{
+  "owner_name": "quoije",
+  "car_model": "Yaris 2013",
+  "device_name": "Yaris OBD",
+  "avatar_path": "img/yaris.png"
+}
 ```
 
-Set it to your preferred name, then restart the app/service.
+| Field | Location | Purpose |
+|-------|----------|---------|
+| `owner_name` | Top-right of app topbar | Your name/username |
+| `car_model` | Left sidebar (next to car icon) | Vehicle model/year |
+| `device_name` | (Reserved) | Future server-side use in Phase 25.5 |
+| `avatar_path` | Top-right avatar circle | Profile picture (relative to `static/`) |
 
-> Important: `account.name` is also used in the local SQLite filename (`db/sql/<name>_<car>.db` via [modules/app_sql.py](./modules/app_sql.py)).  
-> If you already have trip data and change the name, the app will create a new DB file unless you rename/migrate the existing one.
+After editing, restart the app:
 
-### Change profile picture
+```bash
+# If running as a systemd service:
+sudo systemctl restart yaris-obd.service
 
-Current avatar is hardcoded in [templates/base.html](./templates/base.html) to:
-
-```html
-src="{{ url_for('static', filename='img/yaris.png') }}"
+# If running manually:
+# Ctrl+C and python3 app.py
 ```
 
-Simplest option: replace [static/img/yaris.png](./static/img/yaris.png) with your image (same filename/path).  
-Alternative: edit the `filename='img/yaris.png'` value in [templates/base.html](./templates/base.html).
+### Changing the profile picture
+
+Option 1: Replace the default image file:
+```bash
+cp /path/to/your/image.png static/img/yaris.png
+```
+
+Option 2: Add your image to `static/img/` and update `avatar_path`:
+```json
+{
+  "avatar_path": "img/my-avatar.png"
+}
+```
+
+### Important: Username and database filename
+
+The local SQLite database filename is based on `owner_name`: `db/sql/<owner_name>_<car_model>.db` (via [modules/app_sql.py](./modules/app_sql.py)).
+
+If you **change `owner_name`** and already have trip data:
+- The app will create a **new database** with the new name
+- Your old database remains at `db/sql/quoije_Yaris2013.db` (orphaned)
+
+To preserve your data:
+```bash
+# Option 1: Rename the database file
+mv db/sql/quoije_Yaris2013.db "db/sql/YourName_YourCar.db"
+
+# Option 2: Start fresh
+rm db/sql/quoije_Yaris2013.db
+```
 
 ## Project status