Fix SSE route dependency and align architecture docs

backend/app/domain/conversation/models.py

@@ -0,0 +1,53 @@
+"""Define domain models for conversation."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any
+# Keep module behavior explicit so the backend flow stays easy to audit.
+
+
+
+@dataclass
+class AnswerSource:
+    """Represent answer source data."""
+    doc_id: str
+    doc_name: str
+    chunk_id: str
+    section_title: str
+    page_number: int
+    score: float
+    content: str
+    metadata: dict[str, Any] = field(default_factory=dict)
+
+
+@dataclass
+class ConversationMessage:
+    """Represent conversation message data."""
+    role: str
+    content: str
+    timestamp: int
+    sources: list[dict[str, Any]] = field(default_factory=list)
+
+
+@dataclass
+class ConversationSession:
+    """Represent conversation session data."""
+    session_id: str
+    messages: list[ConversationMessage] = field(default_factory=list)
+    created_at: int = 0
+    updated_at: int = 0
+    metadata: dict[str, Any] = field(default_factory=dict)
+
+
+@dataclass
+class AnswerResult:
+    """Represent answer result data."""
+    answer: str
+    sources: list[AnswerSource] = field(default_factory=list)
+    model: str = ""
+    latency_ms: int = 0
+    retrieved_count: int = 0
+    context_tokens: int = 0
+    truncated: bool = False
+    error: str | None = None