feat(chat): add random public_id and fix users blocked route

- add chats.public_id random identifier with migration 0011
- expose public_id in chat API payloads
- use chat public_id in message search UI label
- fix users router order so /users/blocked no longer conflicts with /users/{user_id}

web/src/chat/types.ts

@@ -4,6 +4,7 @@ export type DeliveryStatus = "sending" | "sent" | "delivered" | "read";
 
 export interface Chat {
   id: number;
+  public_id: string;
   type: ChatType;
   title: string | null;
   display_title?: string | null;