Fix hashtag preferences loading and profile persistence issues

- Migrated Kind 0 profile metadata storage to unified `profileCache.js` with partitioning and persistence.
- Added `defaultDTag` for hashtag preferences in `cachePolicies.js` to ensure consistent key resolution.
- Updated `hashtagPreferencesService.js` to use `profileCache` and implemented legacy data migration.
- Added `handleEvent` to `NostrClient` to centrally ingest Kind 0 events into the cache.
- Updated `authService.js` and `cache.js` to delegate profile operations to the unified cache system.
- Added `PROFILE_METADATA` schema to `nostrEventSchemas.js`.

js/nostrEventSchemas.js

@@ -28,6 +28,7 @@ export const NOTE_TYPES = Object.freeze({
   ADMIN_BLACKLIST: "adminBlacklist",
   ADMIN_WHITELIST: "adminWhitelist",
   STORAGE_CHALLENGE: "storageChallenge",
+  PROFILE_METADATA: "profileMetadata",
 });
 
 export const SUBSCRIPTION_LIST_IDENTIFIER = "subscriptions";
@@ -459,6 +460,16 @@ const BASE_SCHEMAS = {
         "Ephemeral challenge event used for key derivation; never published.",
     },
   },
+  [NOTE_TYPES.PROFILE_METADATA]: {
+    type: NOTE_TYPES.PROFILE_METADATA,
+    label: "Profile metadata",
+    kind: 0,
+    appendTags: DEFAULT_APPEND_TAGS,
+    content: {
+      format: "json",
+      description: "Standard NIP-01 profile metadata (name, about, picture, etc.).",
+    },
+  },
 };
 
 let schemaOverrides = {};