fix GC [no key], camera-off avatar, timestamps, GC remove error handling

- GC [no key]: cache own public key in pubKeyCache on app init
(setupSession + completeGoogleSetup) so sendGroupMsg always has
the sender's key to wrap the AES key. Without this, encrypted_aes_key
for self was missing and the echo showed [Encrypted message].
- Camera-off avatar: local video avatar now uses me.display_name/avatar_color
instead of callTarget (which was showing the other person's avatar
even when YOUR camera was off).
- Timestamps always 'now': changed str(msg.created_at) to
msg.created_at.isoformat() so JS Date parses correctly regardless
of timezone, fixing the 2-minutes-ago-showing-as-now bug.
- GC remove: added try/catch to removeFromGroup so silent failures
don't leave stale UI

src/chat.py

@@ -75,7 +75,7 @@ def list_conversations(request: Request, db: Session = Depends(get_db)):
         result.append({
             "id": conv.id,
             "other_user": user_to_dict(other),
-            "last_message_at": str(last_msg.created_at) if last_msg else None,
+            "last_message_at": last_msg.created_at.isoformat() if last_msg and hasattr(last_msg.created_at, 'isoformat') else str(last_msg.created_at) if last_msg else None,
             "unread_count": sum(1 for msg in conv.messages if not msg.is_read and msg.sender_id != me.id)
         })
     result.sort(key=lambda x: x["last_message_at"] or "", reverse=True)
@@ -193,7 +193,7 @@ def msg_to_dict(msg: Message, viewer_id: int) -> dict:
         "sender_id": msg.sender_id,
         "sender_name": msg.sender.display_name if msg.sender else "Unknown",
         "ciphertext": msg.ciphertext_for_sender if is_sender else msg.ciphertext_for_recipient,
-        "created_at": str(msg.created_at),
+        "created_at": msg.created_at.isoformat() if hasattr(msg.created_at, 'isoformat') else str(msg.created_at),
         "is_read": msg.is_read,
     }
 
@@ -206,7 +206,7 @@ def group_msg_to_dict(msg: GroupMessage, viewer_id: int) -> dict:
         "ciphertext": msg.ciphertext,
         "iv": msg.iv,
         "encrypted_aes_key": keys.get(str(viewer_id)),
-        "created_at": str(msg.created_at),
+        "created_at": msg.created_at.isoformat() if hasattr(msg.created_at, 'isoformat') else str(msg.created_at),
     }
 
 def group_to_dict(group: Group, viewer_id: int) -> dict:
@@ -217,5 +217,5 @@ def group_to_dict(group: Group, viewer_id: int) -> dict:
         "created_by": group.created_by,
         "avatar_color": group.avatar_color,
         "member_count": len(group.members),
-        "created_at": str(group.created_at),
+        "created_at": group.created_at.isoformat() if hasattr(group.created_at, 'isoformat') else str(group.created_at),
     }

src/static/app.js

@@ -87,6 +87,11 @@ async function setupSession(tok, generateKeys = false) {
       me.public_key = pubKeyStr;
     }
 
+    // Cache our own public key for group message encryption
+    if (me.public_key) {
+      try { pubKeyCache[me.id] = await Crypto.importPublicKey(me.public_key); } catch (e) {}
+    }
+
     showApp();
     updateMyProfile();
     await loadChats();
@@ -247,6 +252,9 @@ async function completeGoogleSetup() {
     const pubKeyStr = JSON.stringify(kp.publicKeyJwk);
     await apiFetch("/auth/profile", token, "PUT", { public_key: pubKeyStr });
     me.public_key = pubKeyStr;
+    if (me.public_key) {
+      try { pubKeyCache[me.id] = await Crypto.importPublicKey(me.public_key); } catch (e) {}
+    }
     showApp();
     updateMyProfile();
     try { await loadChats(); } catch (e) { console.error("loadChats error:", e); }
@@ -659,13 +667,13 @@ function cleanupCall() {
 function setupCallMedia() {
   const lv = document.getElementById("local-video");
   if (lv) lv.srcObject = localStream;
-  // Init local avatar
+  // Init local avatar (shows me when my camera is off)
   const localInner = document.getElementById("local-video-avatar-inner");
-  if (localInner && callTarget) {
-    localInner.textContent = callTarget.display_name[0].toUpperCase();
-    localInner.style.background = callTarget.avatar_color || "#6366f1";
+  if (localInner && me) {
+    localInner.textContent = me.display_name[0].toUpperCase();
+    localInner.style.background = me.avatar_color || "#6366f1";
   }
-  // Init remote avatar
+  // Init remote avatar (shows other person when their camera is off)
   const remoteInner = document.getElementById("remote-video-avatar-inner");
   if (remoteInner && callTarget) {
     remoteInner.textContent = callTarget.display_name[0].toUpperCase();
@@ -1206,7 +1214,12 @@ async function addToGroup(userId) {
 }
 
 async function removeFromGroup(userId) {
-  await apiFetch(`/chat/groups/${currentGroupData.id}/members/${userId}`, token, "DELETE");
+  try {
+    await apiFetch(`/chat/groups/${currentGroupData.id}/members/${userId}`, token, "DELETE");
+  } catch (e) {
+    console.error("removeFromGroup error:", e);
+    return;
+  }
   if (userId === me.id) {
     closeModal("modal-group-settings");
     currentChat = null;