feat: inject PSA ticket context into copilot system prompt (Task 10)

When a copilot conversation has an associated session with a linked PSA
ticket, fetch the ticket context and append it to the system prompt.
Failure is non-critical — errors are logged and the copilot proceeds
without context rather than failing the request.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/copilot_service.py

@@ -180,6 +180,40 @@ async def send_message(
     system_prompt += _build_flow_context(tree, conversation.current_node_id)
     system_prompt += build_rag_context(rag_results)
 
+    # Inject PSA ticket context if session has a linked ticket
+    if conversation.session_id:
+        try:
+            from app.models.session import Session as SessionModel
+            session_result = await db.execute(
+                select(SessionModel).where(SessionModel.id == conversation.session_id)
+            )
+            session = session_result.scalar_one_or_none()
+            if session and session.psa_ticket_id:
+                try:
+                    from app.services.psa.registry import get_provider_for_account
+                    from app.services.psa.ticket_context import format_ticket_context_for_prompt
+
+                    provider = await get_provider_for_account(conversation.account_id, db)
+                    connection_id = str(session.psa_connection_id) if session.psa_connection_id else None
+                    ticket_ctx = await provider.get_ticket_context(
+                        ticket_id=int(session.psa_ticket_id),
+                        connection_id=connection_id,
+                    )
+                    system_prompt += "\n\n" + format_ticket_context_for_prompt(ticket_ctx)
+                except Exception as psa_err:
+                    logger.warning(
+                        "Failed to fetch PSA ticket context for copilot (session=%s, ticket=%s): %s",
+                        conversation.session_id,
+                        session.psa_ticket_id,
+                        psa_err,
+                    )
+        except Exception as session_err:
+            logger.warning(
+                "Failed to look up session for copilot PSA context (session_id=%s): %s",
+                conversation.session_id,
+                session_err,
+            )
+
     # Build messages for AI
     ai_messages = []
     for msg in conversation.messages: