feat: implement board device service with CRUD operations and validation

- Add boardDeviceService for managing device pairing, status, claiming, and revocation.
- Introduce boardDeviceSettings for default settings and validation logic.
- Create integration tests for device lifecycle, concurrent claims, and updates.
- Add unit tests for device pairing, claiming, and settings validation.
- Implement API tests for device endpoints with JWT authentication.
- Develop in-memory repository for testing purposes.
- Create frontend components for managing devices, including a form for device settings.
- Style DevicesPage with CSS for better user experience.

backend/migrations/016_board_devices.sql

@@ -0,0 +1,28 @@
+BEGIN;
+CREATE TABLE IF NOT EXISTS board_pairings (
+  code CHAR(4) PRIMARY KEY CHECK (code ~ '^[0-9]{4}$'),
+  token_hash CHAR(64) NOT NULL UNIQUE,
+  device_info JSONB NOT NULL DEFAULT '{}',
+  expires_at TIMESTAMPTZ NOT NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS board_pairings_expiry ON board_pairings(expires_at);
+CREATE TABLE IF NOT EXISTS board_devices (
+  id UUID PRIMARY KEY,
+  name VARCHAR(100) NOT NULL,
+  city_id INTEGER NOT NULL REFERENCES cities(id) ON DELETE RESTRICT,
+  stop_id INTEGER NOT NULL REFERENCES stops(id) ON DELETE RESTRICT,
+  token_hash CHAR(64) NOT NULL UNIQUE,
+  settings JSONB NOT NULL,
+  revision INTEGER NOT NULL DEFAULT 1 CHECK (revision > 0),
+  applied_revision INTEGER NOT NULL DEFAULT 0 CHECK (applied_revision >= 0 AND applied_revision <= revision),
+  last_seen_at TIMESTAMPTZ,
+  device_info JSONB NOT NULL DEFAULT '{}',
+  created_by INTEGER REFERENCES users(id) ON DELETE SET NULL,
+  updated_by INTEGER REFERENCES users(id) ON DELETE SET NULL,
+  revoked_at TIMESTAMPTZ,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS board_devices_city ON board_devices(city_id, created_at);
+COMMIT;