Add reverse geocoding location support and fix NoneType error

- Add location template inputs (common_location_template, location_if_unique_template, location_format)
- Display common location in header when all assets share the same location
- Show per-asset location when locations differ using {location_if_unique}
- Location only shown when all three fields (city, state, country) are present
- Fix TypeError on NoneType length check when asset.created_at is null
- Add defensive checks for date parsing to prevent template errors

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

manifest.json

@@ -1,3 +1,3 @@
 {
-  "version": "1.20.0"
+  "version": "1.21.0"
 }