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/models/assistant_chat.py

@@ -49,6 +49,15 @@ class AssistantChat(Base):
     pinned: Mapped[bool] = mapped_column(
         Boolean, nullable=False, default=False
     )
+    conclusion_outcome: Mapped[Optional[str]] = mapped_column(
+        String(20), nullable=True
+    )
+    conclusion_summary: Mapped[Optional[str]] = mapped_column(
+        String, nullable=True
+    )
+    concluded_at: Mapped[Optional[datetime]] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
     )

backend/app/models/survey_response.py

@@ -2,7 +2,7 @@
 import uuid
 from datetime import datetime, timezone
 
-from sqlalchemy import Column, DateTime, ForeignKey, String, Text
+from sqlalchemy import Boolean, Column, DateTime, ForeignKey, String, Text
 from sqlalchemy.dialects.postgresql import JSONB, UUID
 
 from app.core.database import Base
@@ -17,4 +17,6 @@ class SurveyResponse(Base):
     ip_address = Column(String(45), nullable=True)
     user_agent = Column(Text, nullable=True)
     invite_id = Column(UUID(as_uuid=True), ForeignKey("survey_invites.id"), nullable=True)
+    is_read = Column(Boolean, nullable=False, default=False)
+    archived_at = Column(DateTime(timezone=True), nullable=True)
     created_at = Column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), nullable=False)