docs(03-04): complete usage & cost dashboard plan

- Added Recharts cost tracking dashboard at /usage/[tenantId]
- UsageChart, ProviderCostChart, MessageVolumeChart components
- BudgetAlertBadge with ok/warning/exceeded color coding
- TanStack Query hooks for usage summary, provider costs, message volume, budget alerts
- Time range selector (Last 7/30 days, This month, Last 3 months)
- Usage nav link and /usage tenant picker index page
- Installed recharts (was in package.json but missing from node_modules)
- Portal builds cleanly with /usage and /usage/[tenantId] routes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.planning/STATE.md

@@ -3,14 +3,14 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: executing
-stopped_at: "Stopped at checkpoint:human-verify in 03-03-PLAN.md (Task 2)"
-last_updated: "2026-03-24T03:47:11.921Z"
+stopped_at: "Completed 03-04-PLAN.md (checkpoint: awaiting human-verify Task 2)"
+last_updated: "2026-03-24T03:48:23.065Z"
 last_activity: 2026-03-23 — Completed 02-05 multimodal media support and WhatsApp outbound routing
 progress:
   total_phases: 3
   completed_phases: 2
   total_plans: 14
-  completed_plans: 12
+  completed_plans: 13
   percent: 78
 ---
 
@@ -62,6 +62,7 @@ Progress: [████████░░] 78%
 | Phase 02-agent-features P06 | 9m 53s | 2 tasks | 3 files |
 | Phase 03-operator-experience P01 | 22m | 3 tasks | 20 files |
 | Phase 03-operator-experience P03 | ~8m | 1 tasks | 6 files |
+| Phase 03-operator-experience P04 | 10m | 1 tasks | 8 files |
 
 ## Accumulated Context
 
@@ -113,6 +114,9 @@ Recent decisions affecting current work:
 - [Phase 03-operator-experience]: window.location.href for Stripe redirects (not router.push) — Stripe Checkout/Portal URLs are external domains
 - [Phase 03-operator-experience]: use(searchParams) in client components for Next.js 15 — searchParams is a Promise, must be unwrapped with React.use()
 - [Phase 03-operator-experience]: BillingStatus uses inline Tailwind color classes — existing Badge variants lack semantic blue/green/amber/red states needed for subscription status
+- [Phase 03-operator-experience]: recharts installed with --force due to npm ENOTEMPTY race bug — was in package.json but not node_modules
+- [Phase 03-operator-experience]: Usage nav links to /usage tenant picker (not hardcoded tenantId) — supports multi-tenant operators
+- [Phase 03-operator-experience]: BudgetAlertBadge renders neutral 'No limit set' for null budget_limit_usd — prevents false alarms
 
 ### Pending Todos
 
@@ -124,6 +128,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-03-24T03:47:11.918Z
-Stopped at: Stopped at checkpoint:human-verify in 03-03-PLAN.md (Task 2)
+Last session: 2026-03-24T03:48:23.062Z
+Stopped at: Completed 03-04-PLAN.md (checkpoint: awaiting human-verify Task 2)
 Resume file: None