feat: downloads tab + public Movies/yaris-obd/ folder

- Downloads now go to Movies/yaris-obd/ (visible in file managers)
- New Downloads tab: list downloaded files, tap to play (system player),
  delete button
- FileProvider added for video playback intent
- Downloaded files auto-refresh after each download

android/app/src/main/AndroidManifest.xml

@@ -36,6 +36,16 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+
+        <provider
+            android:name="androidx.core.content.FileProvider"
+            android:authorities="${applicationId}.fileprovider"
+            android:exported="false"
+            android:grantUriPermissions="true">
+            <meta-data
+                android:name="android.support.FILE_PROVIDER_PATHS"
+                android:resource="@xml/file_paths" />
+        </provider>
     </application>
 
 </manifest>