fix(starlark): blank app locations use the device location, not San Francisco

A Starlark (Tidbyt) app whose Location field is blank rendered at its
author's hard-coded DEFAULT_LOCATION -- usually San Francisco -- even with
the device city set under General settings. A user in Charlotte, NC got San
Francisco weather and radar with nothing in config.json to explain it.

src/device_location.py fills unset location fields at render time (display
plugin and the web standalone render): the device city is geocoded once via
Open-Meteo, preferring a match in the configured state/country, and cached
permanently. A saved location always wins; if the lookup fails the field is
dropped so the app uses its own default, and the failure is not retried for
30 minutes.

Also fixes the config form: clearing a location omitted the key, and the
save merges, so the old value could never be removed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web_interface/blueprints/api_v3/__init__.py

@@ -49,6 +49,7 @@ from src.web_interface.validators import (
 from src.error_aggregator import get_error_aggregator
 from src.common.permission_utils import install_requirements_file
 from src.common.path_safety import resolve_under
+from src.device_location import DeviceLocationResolver, apply_device_location
 _SUDO = shutil.which('sudo')
 _JOURNALCTL = shutil.which('journalctl')
 _GIT = shutil.which('git')
@@ -1719,6 +1720,32 @@ def _validate_starlark_app_path(app_id: str) -> Tuple[Optional[Path], Optional[s
     except OSError as e:
         logger.warning("Path validation error for app_id %r: %s", app_id, e)
         return None, "Invalid app_id"
+_starlark_device_location: Optional[DeviceLocationResolver] = None
+
+
+def _get_starlark_device_location() -> DeviceLocationResolver:
+    """One resolver per process, so a geocode failure's backoff is shared."""
+    global _starlark_device_location
+    if _starlark_device_location is None:
+        _starlark_device_location = DeviceLocationResolver(
+            getattr(api_v3, 'cache_manager', None) or _ensure_cache_manager(), logger)
+    return _starlark_device_location
+
+
+def _read_starlark_schema(app_dir: Path) -> Optional[Dict[str, Any]]:
+    """An installed app's schema.json, or None if it has none or it's unreadable."""
+    schema_file = app_dir / 'schema.json'
+    if not schema_file.exists():
+        return None
+    try:
+        with open(schema_file) as f:
+            schema = json.load(f)
+    except (OSError, json.JSONDecodeError) as e:
+        logger.warning("Could not read schema.json at %s: %s", schema_file, e)
+        return None
+    return schema if isinstance(schema, dict) else None
+
+
 def _standalone_render_starlark_app(app_id: str) -> Tuple[bool, int, Optional[str]]:
     """Render a Starlark app via pixlet directly (no plugin required).
 
@@ -1790,6 +1817,9 @@ def _standalone_render_starlark_app(app_id: str) -> Tuple[bool, int, Optional[st
 
     INTERNAL_KEYS = {'render_interval', 'display_duration'}
     pixlet_config = {k: v for k, v in app_config.items() if k not in INTERNAL_KEYS}
+    pixlet_config = apply_device_location(
+        pixlet_config, _read_starlark_schema(app_dir),
+        _get_starlark_device_location(), full_config)
 
     output_path = str(app_dir / 'cached_render.webp')
     cmd = [pixlet_path, 'render', str(star_file)]

web_interface/templates/v3/partials/starlark_config.html

@@ -221,6 +221,7 @@
                                    data-starlark-location-key="timezone">
                         </div>
                     </div>
+                    <p class="text-xs text-gray-500 mt-1">Leave latitude and longitude blank to use this device's location (City / State / Country in General settings).</p>
                     {% if field_desc %}
                     <p class="text-xs text-gray-400 mt-1">{{ field_desc }}</p>
                     {% endif %}
@@ -421,9 +422,10 @@ function saveStarlarkConfig(appId) {
             var locKey = sub.getAttribute('data-starlark-location-key');
             if (sub.value) loc[locKey] = sub.value;
         });
-        if (Object.keys(loc).length > 0) {
-            config[fieldId] = JSON.stringify(loc);
-        }
+        // Blank still has to be sent: the save merges into the stored config,
+        // so leaving the key out kept the old location with no way to clear
+        // it back to the device's.
+        config[fieldId] = Object.keys(loc).length > 0 ? JSON.stringify(loc) : '';
     });
 
     fetch('/api/v3/starlark/apps/' + encodeURIComponent(appId) + '/config', {