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/schemas/survey.py

@@ -46,6 +46,12 @@ class SurveyInviteStatus(BaseModel):
     status: str
 
 
+class SurveyEmailCopyRequest(BaseModel):
+    """Request to email a copy of responses to the respondent."""
+    email: str = Field(..., max_length=255)
+    response_id: str
+
+
 class SurveyResponseDetail(BaseModel):
     """Full survey response returned to admin."""
     id: str
@@ -53,6 +59,8 @@ class SurveyResponseDetail(BaseModel):
     responses: dict[str, Any]
     source: str
     invite_name: Optional[str]
+    is_read: bool = False
+    archived_at: Optional[datetime] = None
     created_at: datetime
 
 
@@ -61,3 +69,4 @@ class SurveyResponseListResponse(BaseModel):
     responses: list[SurveyResponseDetail]
     total: int
     this_week: int
+    unread: int