refactor: use proper applesauce-loaders for NIP-51 bookmark fetching

- Replace manual event fetching with applesauce Address Loader
- Use Loaders.createAddressLoader() for proper replaceable event loading
- Configure loader with eventStore, bufferTime, and relay hints
- Remove manual RxJS subscription handling in favor of applesauce patterns
- Add applesauce-loaders dependency for specialized loading methods
- Clean up unused imports and variables
- Follow applesauce best practices for event loading

This implements the proper applesauce pattern for fetching kind:10003
bookmark events as recommended in the applesauce-loaders documentation.

node_modules/.package-lock.json

@@ -1921,6 +1921,22 @@
         "url": "lightning:nostrudel@geyser.fund"
       }
     },
+    "node_modules/applesauce-loaders": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/applesauce-loaders/-/applesauce-loaders-3.1.0.tgz",
+      "integrity": "sha512-9IY5RYqoXcIgAAdJNuMjMBr+CI85z1yj708C92UiP9YMQ4mrIIEvZbMmWLApBzRn5XsmmEa00a/iNlXpkRg9Sw==",
+      "license": "MIT",
+      "dependencies": {
+        "applesauce-core": "^3.1.0",
+        "nanoid": "^5.0.9",
+        "nostr-tools": "~2.15",
+        "rxjs": "^7.8.1"
+      },
+      "funding": {
+        "type": "lightning",
+        "url": "lightning:nostrudel@geyser.fund"
+      }
+    },
     "node_modules/applesauce-react": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/applesauce-react/-/applesauce-react-3.1.0.tgz",