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/schemas.py

@@ -11,6 +11,10 @@ class ChatRead(BaseModel):
     id: int
     type: ChatType
     title: str | None = None
+    handle: str | None = None
+    description: str | None = None
+    is_public: bool = False
+    is_saved: bool = False
     pinned_message_id: int | None = None
     created_at: datetime
 
@@ -31,6 +35,9 @@ class ChatDetailRead(ChatRead):
 class ChatCreateRequest(BaseModel):
     type: ChatType
     title: str | None = Field(default=None, max_length=255)
+    handle: str | None = Field(default=None, max_length=64)
+    description: str | None = Field(default=None, max_length=512)
+    is_public: bool = False
     member_ids: list[int] = Field(default_factory=list)
 
 
@@ -48,3 +55,11 @@ class ChatTitleUpdateRequest(BaseModel):
 
 class ChatPinMessageRequest(BaseModel):
     message_id: int | None = None
+
+
+class ChatDeleteRequest(BaseModel):
+    for_all: bool = False
+
+
+class ChatDiscoverRead(ChatRead):
+    is_member: bool