Fix/geohash blocks (#483)

* fix(geo-block): enable block/unblock for geohash users and enforce blocks\n\n- Add persisted set of blocked Nostr pubkeys in SecureIdentityStateManager\n- Check Nostr blocks for incoming messages (public + geo DMs)\n- Prevent sending geo DMs to blocked users\n- Extend /block and /unblock to resolve geohash display names to pubkeys and act accordingly\n- Improve /block list to show geohash blocks (visible names or #suffix)

* fix(geo-block): enforce blocks on geohash public and DM receive; add block/unblock actions to geohash people list

* fix: mark handlePublicMessage as @MainActor to call isMessageBlocked safely

* ui(block): show blocked indicator (nosign icon) next to blocked peers in mesh and geohash lists

* fix(geo-block): early-drop blocked pubkeys on geohash receive; filter blocked users from participants list

* fix(geo-block): purge existing geohash messages/DMs on block; block directly from chat using Nostr sender ID when available

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>

bitchat/Identity/IdentityModels.swift

@@ -149,6 +149,9 @@ struct IdentityCache: Codable {
     // Last interaction timestamps (privacy: optional)
     var lastInteractions: [String: Date] = [:] 
     
+    // Blocked Nostr pubkeys (lowercased hex) for geohash chats
+    var blockedNostrPubkeys: Set<String> = []
+    
     // Schema version for future migrations
     var version: Int = 1
 }
@@ -222,4 +225,4 @@ enum ConnectionQuality {
 }
 
 // MARK: - Migration Support
-// Removed LegacyFavorite - no longer needed
+// Removed LegacyFavorite - no longer needed

bitchat/Identity/SecureIdentityStateManager.swift

@@ -335,6 +335,30 @@ class SecureIdentityStateManager {
             self.saveIdentityCache()
         }
     }
+
+    // MARK: - Geohash (Nostr) Blocking
+    
+    func isNostrBlocked(pubkeyHexLowercased: String) -> Bool {
+        queue.sync {
+            return cache.blockedNostrPubkeys.contains(pubkeyHexLowercased.lowercased())
+        }
+    }
+    
+    func setNostrBlocked(_ pubkeyHexLowercased: String, isBlocked: Bool) {
+        let key = pubkeyHexLowercased.lowercased()
+        queue.async(flags: .barrier) {
+            if isBlocked {
+                self.cache.blockedNostrPubkeys.insert(key)
+            } else {
+                self.cache.blockedNostrPubkeys.remove(key)
+            }
+            self.saveIdentityCache()
+        }
+    }
+    
+    func getBlockedNostrPubkeys() -> Set<String> {
+        queue.sync { cache.blockedNostrPubkeys }
+    }
     
     // MARK: - Ephemeral Session Management
     
@@ -464,4 +488,4 @@ class SecureIdentityStateManager {
             return cache.verifiedFingerprints
         }
     }
-}
+}