feat: add saved messages, public chat discovery/join, and chat delete options

- add Saved Messages system chat with dedicated API

- add public group/channel metadata and discover/join endpoints

- add chat delete flow with for_all option and channel-wide delete

- switch message actions to context menu and improve reply/forward visuals

- improve microphone permission handling for voice recording

app/chats/router.py

@@ -5,6 +5,8 @@ from app.auth.service import get_current_user
 from app.chats.schemas import (
     ChatCreateRequest,
     ChatDetailRead,
+    ChatDiscoverRead,
+    ChatDeleteRequest,
     ChatMemberAddRequest,
     ChatMemberRead,
     ChatMemberRoleUpdateRequest,
@@ -15,8 +17,12 @@ from app.chats.schemas import (
 from app.chats.service import (
     add_chat_member_for_user,
     create_chat_for_user,
+    delete_chat_for_user,
+    discover_public_chats_for_user,
+    ensure_saved_messages_chat,
     get_chat_for_user,
     get_chats_for_user,
+    join_public_chat_for_user,
     leave_chat_for_user,
     pin_chat_message_for_user,
     remove_chat_member_for_user,
@@ -40,6 +46,24 @@ async def list_chats(
     return await get_chats_for_user(db, user_id=current_user.id, limit=limit, before_id=before_id, query=query)
 
 
+@router.get("/saved", response_model=ChatRead)
+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)
+
+
+@router.get("/discover", response_model=list[ChatDiscoverRead])
+async def discover_chats(
+    query: str | None = None,
+    limit: int = 30,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> list[ChatDiscoverRead]:
+    return await discover_public_chats_for_user(db, user_id=current_user.id, query=query, limit=limit)
+
+
 @router.post("", response_model=ChatRead)
 async def create_chat(
     payload: ChatCreateRequest,
@@ -49,6 +73,15 @@ async def create_chat(
     return await create_chat_for_user(db, creator_id=current_user.id, payload=payload)
 
 
+@router.post("/{chat_id}/join", response_model=ChatRead)
+async def join_chat(
+    chat_id: int,
+    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)
+
+
 @router.get("/{chat_id}", response_model=ChatDetailRead)
 async def get_chat(
     chat_id: int,
@@ -132,6 +165,16 @@ async def leave_chat(
     await leave_chat_for_user(db, chat_id=chat_id, user_id=current_user.id)
 
 
+@router.delete("/{chat_id}", status_code=status.HTTP_204_NO_CONTENT)
+async def delete_chat(
+    chat_id: int,
+    for_all: bool = False,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> None:
+    await delete_chat_for_user(db, chat_id=chat_id, user_id=current_user.id, payload=ChatDeleteRequest(for_all=for_all))
+
+
 @router.post("/{chat_id}/pin", response_model=ChatRead)
 async def pin_chat_message(
     chat_id: int,