docs(03-01): complete backend foundation plan — billing, encryption, HMAC OAuth, LLM key CRUD, usage aggregation

- Create 03-01-SUMMARY.md with full plan documentation
- Update STATE.md: progress 79%, 4 new decisions, session stopped at 03-01
- Update ROADMAP.md: Phase 3 plan progress (1/4 summaries)
- Update REQUIREMENTS.md: mark AGNT-07, LLM-03, PRTA-03, PRTA-05, PRTA-06 complete

.planning/STATE.md

@@ -3,14 +3,14 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: executing
-stopped_at: Phase 3 context gathered
-last_updated: "2026-03-24T02:06:09.044Z"
+stopped_at: Completed 03-01-PLAN.md
+last_updated: "2026-03-24T03:37:56.910Z"
 last_activity: 2026-03-23 — Completed 02-05 multimodal media support and WhatsApp outbound routing
 progress:
   total_phases: 3
   completed_phases: 2
-  total_plans: 10
-  completed_plans: 10
+  total_plans: 14
+  completed_plans: 11
   percent: 78
 ---
 
@@ -60,6 +60,7 @@ Progress: [████████░░] 78%
 | Phase 02-agent-features P02 | 12m 22s | 3 tasks | 19 files |
 | Phase 02-agent-features P05 | ~25m | 2 tasks | 6 files |
 | Phase 02-agent-features P06 | 9m 53s | 2 tasks | 3 files |
+| Phase 03-operator-experience P01 | 22m | 3 tasks | 20 files |
 
 ## Accumulated Context
 
@@ -104,6 +105,10 @@ Recent decisions affecting current work:
 - [Phase 02-agent-features]: Module-level imports in tasks.py for testability — patchable at orchestrator.tasks.*
 - [Phase 02-agent-features]: Unified extras dict carries channel-specific metadata (Slack + WhatsApp) through entire pipeline
 - [Phase 02-agent-features]: wa_id extracted from sender.user_id in handle_message after model_validate and injected into extras
+- [Phase 03-operator-experience]: AuditEvent ORM attribute renamed from 'metadata' to 'event_metadata' — SQLAlchemy 2.0 DeclarativeBase reserves 'metadata'; mapped_column('metadata') preserves DB column name
+- [Phase 03-operator-experience]: StripeClient(api_key=settings.stripe_secret_key) — new v14+ thread-safe API, not legacy stripe.api_key module-level approach
+- [Phase 03-operator-experience]: Stripe webhook idempotency via StripeEvent INSERT + flush + IntegrityError catch — handles Stripe at-least-once delivery
+- [Phase 03-operator-experience]: LLM key listing returns key_hint (last 4 chars only) — portal displays ...ABCD without decrypting Fernet ciphertext
 
 ### Pending Todos
 
@@ -115,6 +120,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-03-24T02:06:09.042Z
-Stopped at: Phase 3 context gathered
-Resume file: .planning/phases/03-operator-experience/03-CONTEXT.md
+Last session: 2026-03-24T03:37:56.908Z
+Stopped at: Completed 03-01-PLAN.md
+Resume file: None