feat(ai-session): add Phase 2 PSA integration, escalation handoff, and session management

Phase 2 of the FlowPilot-First Pivot connecting AI sessions to ConnectWise PSA:

Slice 1 — PSA Ticket Intake:
- FlowPilotEngine accepts psa_ticket intake with graceful CW API fallback
- Ticket picker on intake screen (refactored TicketPickerModal for dual-mode)
- Ticket context card in session sidebar

Slice 2 — Auto Documentation Push:
- PSA documentation service with resolution/escalation note formatting
- Time entry creation via new ConnectWise provider method
- Automatic retry scheduler (APScheduler, 5min interval, 3 retries)
- PSA push status indicators in frontend with manual retry button
- Member mapping warning when CW member not mapped

Slice 3 — Session Pause/Resume & Escalation Handoff:
- Pause/resume endpoints for same-engineer session bookmarking
- Escalation flow: requesting_escalation status, self-escalation blocked
- Enhanced escalation package with LLM-generated hypotheses/suggestions
- Pickup endpoint with continue/fresh resume modes and briefing step
- Escalation queue (sidebar nav + dedicated page)
- SessionBriefing component with continue/fresh choice UI
- EscalateModal with PSA-aware button text

Slice 4 — Mid-Session Ticket Linking:
- Link ticket retroactively with context injection into system prompt
- Link Ticket button in session sidebar

Slice 5 — FlowPilot PSA Settings:
- Settings tab on IntegrationsPage with 7 configurable options
- Stored as flowpilot_settings JSONB on PsaConnection

Database: 2 migrations (flowpilot_settings, psa_post_log changes, status constraint)

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

backend/app/schemas/ai_session.py

@@ -42,6 +42,7 @@ class AISessionCreateResponse(BaseModel):
     matched_flow_name: str | None = None
     match_score: float | None = None
     first_step: AISessionStepResponse
+    psa_context_status: str | None = None  # loaded | unavailable | None (no PSA)
 
 
 # ── Step interaction ──
@@ -131,6 +132,9 @@ class SessionCloseResponse(BaseModel):
     session_id: UUID
     status: str
     documentation: SessionDocumentation
+    psa_push_status: str = "no_psa"  # sent | pending_retry | no_psa | failed
+    psa_push_error: str | None = None
+    member_mapping_warning: str | None = None
 
 
 class RateSessionRequest(BaseModel):
@@ -139,6 +143,18 @@ class RateSessionRequest(BaseModel):
     feedback: str | None = None
 
 
+class PickupSessionRequest(BaseModel):
+    """Pick up an escalated session as a new engineer."""
+    resume_mode: str = Field("continue", pattern="^(continue|fresh)$")
+    additional_context: str | None = None
+
+
+class LinkTicketRequest(BaseModel):
+    """Link a PSA ticket to an in-progress session."""
+    psa_ticket_id: str
+    psa_connection_id: UUID
+
+
 # ── List / Detail ──
 
 class AISessionSummary(BaseModel):
@@ -151,6 +167,8 @@ class AISessionSummary(BaseModel):
     confidence_tier: str
     step_count: int
     session_rating: int | None = None
+    psa_ticket_id: str | None = None
+    escalation_reason: str | None = None
     created_at: datetime
     resolved_at: datetime | None = None
 
@@ -166,6 +184,9 @@ class AISessionDetail(AISessionSummary):
     resolution_action: str | None = None
     escalation_reason: str | None = None
     session_feedback: str | None = None
+    psa_ticket_id: str | None = None
+    psa_connection_id: UUID | None = None
+    ticket_data: dict[str, Any] | None = None
     steps: list[AISessionStepResponse] = []
 
     model_config = {"from_attributes": True}