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/services/nostrService.js

@@ -635,6 +635,7 @@ export class NostrService {
       logger: userLogger,
     });
     this.dmPreviewCache = new LRUCache({ maxSize: DM_PREVIEW_CACHE_LIMIT });
+    this._dmBlockChecker = null;
     try {
       if (this.moderationService && typeof this.moderationService.setNostrClient === "function") {
         this.moderationService.setNostrClient(this.nostrClient);
@@ -644,6 +645,28 @@ export class NostrService {
     }
   }
 
+  setDmBlockChecker(checker) {
+    this._dmBlockChecker =
+      typeof checker === "function" ? checker : null;
+  }
+
+  _isDmRemoteBlocked(message, actorPubkey) {
+    if (typeof this._dmBlockChecker !== "function") {
+      return false;
+    }
+    try {
+      const actor = normalizeHexPubkey(actorPubkey || this.dmActorPubkey || "");
+      const remote = resolveDirectMessageRemotePubkey(message, actor);
+      if (!remote) {
+        return false;
+      }
+      return this._dmBlockChecker(remote);
+    } catch (error) {
+      devLogger.warn("[nostrService] Block check failed for DM", error);
+      return false;
+    }
+  }
+
   log(...args) {
     try {
       this.logger(...args);
@@ -810,6 +833,13 @@ export class NostrService {
       return null;
     }
 
+    if (this._isDmRemoteBlocked(message, actorPubkey)) {
+      devLogger.log("[nostrService] Skipping persist for blocked DM sender", {
+        id: record.id,
+      });
+      return null;
+    }
+
     try {
       await writeMessages(record);
       const notificationResult = await this.dmNotificationManager.recordMessage({
@@ -876,6 +906,11 @@ export class NostrService {
       return;
     }
 
+    if (this._isDmRemoteBlocked(normalized)) {
+      devLogger.log("[nostrService] Dropping DM from blocked user", { eventId });
+      return;
+    }
+
     this.dmMessageIndex.set(eventId, normalized);
 
     const actor = normalizeHexPubkey(