feat: add user display profiles and fix web context menu UX

backend:

- add required user name and optional bio fields

- extend auth/register and user schemas/services with name/bio

- add alembic migration 0006 with safe backfill name=username

- compute per-user chat display_title for private chats

- keep Saved Messages delete-for-all protections

web:

- registration now includes name

- add profile edit modal (name/username/bio/avatar url)

- show private chat names via display_title

- fix context menus to open near cursor with viewport clamping

- stabilize +/close floating button to remove visual jump

app/chats/router.py

@@ -26,6 +26,8 @@ from app.chats.service import (
     leave_chat_for_user,
     pin_chat_message_for_user,
     remove_chat_member_for_user,
+    serialize_chat_for_user,
+    serialize_chats_for_user,
     update_chat_member_role_for_user,
     update_chat_title_for_user,
 )
@@ -43,7 +45,8 @@ async def list_chats(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> list[ChatRead]:
-    return await get_chats_for_user(db, user_id=current_user.id, limit=limit, before_id=before_id, query=query)
+    chats = await get_chats_for_user(db, user_id=current_user.id, limit=limit, before_id=before_id, query=query)
+    return await serialize_chats_for_user(db, user_id=current_user.id, chats=chats)
 
 
 @router.get("/saved", response_model=ChatRead)
@@ -51,7 +54,8 @@ async def get_saved_messages_chat(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
-    return await ensure_saved_messages_chat(db, user_id=current_user.id)
+    chat = await ensure_saved_messages_chat(db, user_id=current_user.id)
+    return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
 @router.get("/discover", response_model=list[ChatDiscoverRead])
@@ -70,7 +74,8 @@ async def create_chat(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
-    return await create_chat_for_user(db, creator_id=current_user.id, payload=payload)
+    chat = await create_chat_for_user(db, creator_id=current_user.id, payload=payload)
+    return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
 @router.post("/{chat_id}/join", response_model=ChatRead)
@@ -79,7 +84,8 @@ async def join_chat(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
-    return await join_public_chat_for_user(db, chat_id=chat_id, user_id=current_user.id)
+    chat = await join_public_chat_for_user(db, chat_id=chat_id, user_id=current_user.id)
+    return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
 @router.get("/{chat_id}", response_model=ChatDetailRead)
@@ -106,7 +112,8 @@ async def update_chat_title(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
-    return await update_chat_title_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=payload)
+    chat = await update_chat_title_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=payload)
+    return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)
 
 
 @router.get("/{chat_id}/members", response_model=list[ChatMemberRead])
@@ -182,4 +189,5 @@ async def pin_chat_message(
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ) -> ChatRead:
-    return await pin_chat_message_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=payload)
+    chat = await pin_chat_message_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=payload)
+    return await serialize_chat_for_user(db, user_id=current_user.id, chat=chat)