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}

app/chats/models.py

@@ -6,6 +6,7 @@ from sqlalchemy import Boolean, DateTime, Enum as SAEnum, ForeignKey, String, Un
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.database.base import Base
+from app.utils.id_generator import generate_public_id
 
 if TYPE_CHECKING:
     from app.messages.models import Message
@@ -28,6 +29,7 @@ class Chat(Base):
     __tablename__ = "chats"
 
     id: Mapped[int] = mapped_column(primary_key=True, index=True)
+    public_id: Mapped[str] = mapped_column(String(24), unique=True, index=True, nullable=False, default=generate_public_id)
     type: Mapped[ChatType] = mapped_column(SAEnum(ChatType), nullable=False, index=True)
     title: Mapped[str | None] = mapped_column(String(255), nullable=True)
     handle: Mapped[str | None] = mapped_column(String(64), nullable=True, unique=True, index=True)