feat: AI chat session conclusion + survey completion & management

AI Assistant - Conclude Session:
- 3-step modal: select outcome (resolved/escalated/paused), add notes, AI-generated summary
- AI generates structured ticket notes from conversation transcript (PSA-ready format)
- Copy to clipboard for pasting into ticketing systems
- "Resume in New Chat" for paused sessions (pre-loads context into new chat)
- Backend: POST /chats/{id}/conclude endpoint, conclusion_summary/outcome/concluded_at fields
- Migration 048: add conclusion fields to assistant_chats

Survey Completion Flow:
- Email-to-self option after submission (branded HTML email with formatted responses)
- Finish button navigates to /survey/thank-you page
- Thank you page with close-window message and feedback email callout
- Already-submitted state updated with same messaging
- Backend: POST /survey/email-copy public endpoint

Survey Admin Management:
- Read/unread indicators (cyan dot, bold name, auto-mark on expand)
- Unread count stat card
- Per-row context menu: mark read/unread, archive/unarchive, delete
- Bulk actions bar: select all, mark read/unread, archive, delete
- Show Archived toggle to filter archived responses
- Backend: 7 new admin endpoints (read, unread, archive, unarchive, delete, bulk)
- Migration 049: add is_read, archived_at to survey_responses

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/endpoints/assistant_chat.py

@@ -35,6 +35,8 @@ from app.schemas.assistant_chat import (
     ChatUpdateRequest,
     RetentionSettingsResponse,
     RetentionSettingsUpdate,
+    ConcludeChatRequest,
+    ConcludeChatResponse,
 )
 from app.schemas.copilot import SuggestedFlow
 from app.services import assistant_chat_service
@@ -203,6 +205,67 @@ async def post_message(
     )
 
 
+@router.post("/chats/{chat_id}/conclude", response_model=ConcludeChatResponse)
+@limiter.limit("10/minute")
+async def conclude_chat(
+    request: Request,
+    chat_id: UUID,
+    data: ConcludeChatRequest,
+    current_user: Annotated[User, Depends(get_current_active_user)],
+    db: Annotated[AsyncSession, Depends(get_db)],
+    _: None = Depends(require_engineer_or_admin),
+):
+    """Conclude a chat session and generate ticket-ready summary."""
+    _require_ai_enabled()
+
+    result = await db.execute(
+        select(AssistantChat).where(
+            AssistantChat.id == chat_id,
+            AssistantChat.user_id == current_user.id,
+        )
+    )
+    chat = result.scalar_one_or_none()
+    if not chat:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Chat not found")
+
+    if chat.concluded_at:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Chat already concluded",
+        )
+
+    if chat.message_count < 2:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Chat must have at least one exchange before concluding",
+        )
+
+    try:
+        summary = await assistant_chat_service.generate_conclusion_summary(
+            chat=chat,
+            outcome=data.outcome,
+            notes=data.notes,
+        )
+    except Exception as e:
+        logger.exception("Failed to generate conclusion summary: %s", e)
+        raise HTTPException(
+            status_code=status.HTTP_502_BAD_GATEWAY,
+            detail="Failed to generate summary. Please try again.",
+        )
+
+    now = datetime.now(timezone.utc)
+    chat.conclusion_outcome = data.outcome
+    chat.conclusion_summary = summary
+    chat.concluded_at = now
+    await db.commit()
+
+    return ConcludeChatResponse(
+        summary=summary,
+        outcome=data.outcome,
+        concluded_at=now,
+    )
+
+
 @router.patch("/chats/{chat_id}", response_model=ChatDetailResponse)
 async def update_chat(
     chat_id: UUID,