Add sender DID resolution and self-decryption for chat messages

The messages API now resolves and includes sender DIDs for received messages, enabling proper decryption in the chat UI. The chat page adds logic to decrypt self-encrypted messages for sent items and improves V2 envelope handling, while useChatEncryption now serializes ratchet state before storage.

src/app/api/swarm/chat/messages/route.ts

@@ -98,6 +98,38 @@ export async function GET(request: NextRequest) {
     
     console.log('[Messages API] Recipient public key found:', !!recipientPublicKey);
 
+    // Get sender DID for received messages
+    const senderDids = new Map<string, string>();
+    for (const msg of messages) {
+      const isSentByMe = msg.senderHandle === session.user.handle;
+      if (!isSentByMe && !senderDids.has(msg.senderHandle)) {
+        // Try to get DID for this sender
+        try {
+          const isRemote = msg.senderHandle.includes('@');
+          if (isRemote) {
+            const [handle, domain] = msg.senderHandle.split('@');
+            const protocol = domain.includes('localhost') ? 'http' : 'https';
+            const response = await fetch(`${protocol}://${domain}/api/users/${handle}`);
+            if (response.ok) {
+              const data = await response.json();
+              if (data.user?.did) {
+                senderDids.set(msg.senderHandle, data.user.did);
+              }
+            }
+          } else {
+            const senderUser = await db.query.users.findFirst({
+              where: eq(users.handle, msg.senderHandle),
+            });
+            if (senderUser?.did) {
+              senderDids.set(msg.senderHandle, senderUser.did);
+            }
+          }
+        } catch (e) {
+          console.error('[Messages API] Failed to resolve sender DID:', e);
+        }
+      }
+    }
+
     const messagesWithDecryption = messages.map((msg) => {
       const isSentByMe = msg.senderHandle === session.user.handle;
       
@@ -110,6 +142,7 @@ export async function GET(request: NextRequest) {
         senderHandle: msg.senderHandle,
         senderDisplayName: msg.senderDisplayName,
         senderAvatarUrl: msg.senderAvatarUrl,
+        senderDid: isSentByMe ? undefined : senderDids.get(msg.senderHandle), // Add DID for received messages
         // For decryption:
         // - Sent messages: need recipient's public key
         // - Received messages: need sender's public key