feat(chat): add citation entry data shapes

surfsense_backend/app/agents/chat/multi_agent_chat/shared/citations/models.py

@@ -0,0 +1,31 @@
+"""Data shapes for the citation registry."""
+
+from __future__ import annotations
+
+from enum import Enum
+from typing import Any
+
+from pydantic import BaseModel, Field
+
+
+class CitationSourceType(str, Enum):
+    """Source kind of a citable unit; the value is the stable wire/dedup form."""
+
+    KB_CHUNK = "kb_chunk"
+    KB_DOCUMENT = "kb_document"
+    CONNECTOR_ITEM = "connector_item"
+    WEB_RESULT = "web_result"
+    CHAT_TURN = "chat_turn"
+    ANON_CHUNK = "anon_chunk"
+
+
+class CitationEntry(BaseModel):
+    """A registered unit: ``n`` (the label), ``locator`` (identity), ``display`` (UI only)."""
+
+    n: int
+    source_type: CitationSourceType
+    locator: dict[str, Any]
+    display: dict[str, Any] = Field(default_factory=dict)
+
+
+__all__ = ["CitationEntry", "CitationSourceType"]