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/alembic/versions/cc3201489b72_add_requesting_escalation_status.py

@@ -0,0 +1,35 @@
+"""add requesting_escalation status
+
+Revision ID: cc3201489b72
+Revises: bb2101378a61
+Create Date: 2026-03-18 23:30:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = 'cc3201489b72'
+down_revision: Union[str, None] = 'bb2101378a61'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Drop old status constraint and recreate with new values
+    op.drop_constraint('ck_ai_sessions_status', 'ai_sessions', type_='check')
+    op.create_check_constraint(
+        'ck_ai_sessions_status',
+        'ai_sessions',
+        "status IN ('active', 'paused', 'resolved', 'escalated', 'requesting_escalation', 'abandoned')",
+    )
+
+
+def downgrade() -> None:
+    op.drop_constraint('ck_ai_sessions_status', 'ai_sessions', type_='check')
+    op.create_check_constraint(
+        'ck_ai_sessions_status',
+        'ai_sessions',
+        "status IN ('active', 'paused', 'resolved', 'escalated', 'abandoned')",
+    )