fix: resolve cross-platform SQLite JSON parsing inconsistencies

- Add platform-agnostic parseJsonField utility to handle different SQLite implementations
- Web SQLite (wa-sqlite/absurd-sql) auto-parses JSON strings to objects
- Capacitor SQLite returns raw strings requiring manual parsing
- Update searchBoxes parsing to use new utility for consistent behavior
- Fixes "[object Object] is not valid JSON" error when switching platforms
- Ensures compatibility between web and mobile SQLite implementations

Fixes: searchBoxes parsing errors in databaseUtil.ts
Related: contactMethods field has similar issue (needs same treatment)

src/views/SearchAreaView.vue

@@ -215,7 +215,7 @@ export default class SearchAreaView extends Vue {
         if (USE_DEXIE_DB) {
           await db.open();
           await db.settings.update(MASTER_SETTINGS_KEY, {
-            searchBoxes: [newSearchBox],
+            searchBoxes: searchBoxes as any,  // Type assertion for Dexie compatibility
           });
         }
         this.searchBox = newSearchBox;
@@ -269,7 +269,7 @@ export default class SearchAreaView extends Vue {
       if (USE_DEXIE_DB) {
         await db.open();
         await db.settings.update(MASTER_SETTINGS_KEY, {
-          searchBoxes: [],
+          searchBoxes: "[]" as any,  // Type assertion for Dexie compatibility
           filterFeedByNearby: false,
         });
       }