fix: apply block/mute list filtering to DM messages and conversations

The user's block/mute list (NIP-51) was not being checked when
processing direct messages, allowing blocked users' messages to appear
in conversations, trigger notifications, and increment unseen counts.

This adds block filtering at four layers:
- nostrService.applyDirectMessage: drops incoming DMs from blocked users
  before they enter the in-memory message cache
- nostrService.persistDirectMessageRecord: prevents blocked DM senders
  from being persisted to IndexedDB or triggering notifications
- profileModalController.buildDmConversationData: filters blocked users
  from the conversation list UI (catches pre-block persisted messages)
- applicationBootstrap: excludes blocked-user conversations from the
  unread DM badge count

The block checker is injected via setDmBlockChecker() to keep
nostrService decoupled from userBlocks, wired up in app.js init().

https://claude.ai/code/session_01EAVLtAM14GN99Eik8otLg2

js/ui/profileModalController.js

@@ -4197,7 +4197,15 @@ export class ProfileModalController {
       };
     }
 
-    const threads = this.groupDirectMessages(messages, actor);
+    const allThreads = this.groupDirectMessages(messages, actor);
+    const blocksService = this.services.userBlocks;
+    const isRemoteBlocked =
+      blocksService && typeof blocksService.isBlocked === "function"
+        ? (pubkey) => blocksService.isBlocked(pubkey)
+        : () => false;
+    const threads = allThreads.filter(
+      (thread) => !thread.remoteHex || !isRemoteBlocked(thread.remoteHex),
+    );
     const remoteKeys = new Set();
     threads.forEach((thread) => {
       if (thread.remoteHex) {