chore(services): rename services/provisioning -> services/platform-api

O.0 prep from OPERATOR-PLAN.md. Mechanical refactor before adding partner
management and operator-specific endpoints. The service now owns more than
just provisioning orchestration (it'll soon own partners, tenant lifecycle
actions, multi-audience JWT validation), so the name 'platform-api' reflects
its scope better.

What changed:
- Directory: services/provisioning/ -> services/platform-api/
- Package: @dezky/provisioning -> @dezky/platform-api
- Docker: container_name dezky-provisioning -> dezky-platform-api;
  compose service key 'provisioning' -> 'platform-api'; volume
  provisioning_node_modules -> platform_api_node_modules
- Portal: PROVISIONING_INTERNAL_URL env var -> PLATFORM_API_INTERNAL_URL,
  default URL http://provisioning:3001 -> http://platform-api:3001 in all
  three proxy routes (me.get.ts, tenants/index.post.ts, tenants/[slug]/
  reconcile.post.ts), plus NUXT_API_BASE updated
- Health endpoint service identifier and main.ts log lines updated to
  'dezky-platform-api'
- Docs swept: README, CLAUDE.md, SERVICES.md, AUTHENTIK-SETUP.md,
  NEXT-STEPS.md, TROUBLESHOOTING.md, OPERATOR-PLAN.md, traefik/dynamic.yml

What deliberately stays:
- Internal module names ProvisioningService / ProvisioningModule (those
  describe an orchestration sub-concern, not the service's purpose)
- Tenant.provisioningStatus / provisioningErrors field names (state
  per integration, not service name)
- File services/platform-api/src/tenants/provisioning.service.ts
- 'Hetzner provisioning' references in production-prep docs (infrastructure
  provisioning, unrelated)

Verified end-to-end after rename: /api/me returns 200 with profile + 2
tenants + subscription, /api/tenants/dezky/reconcile returns 200 with
Authentik integration still ok.

OPERATOR-PLAN.md O.0 checkboxes ticked.

services/platform-api/src/main.ts

@@ -0,0 +1,39 @@
+// Dezky platform API — Entry point.
+// Owns the platform control plane: tenants, partners, users, subscriptions,
+// plus the provisioning orchestration (Authentik / Stalwart / OCIS).
+
+import { ValidationPipe } from '@nestjs/common'
+import { NestFactory } from '@nestjs/core'
+import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify'
+import { AppModule } from './app.module.js'
+
+async function bootstrap() {
+  const app = await NestFactory.create<NestFastifyApplication>(
+    AppModule,
+    new FastifyAdapter({ logger: true }),
+  )
+
+  app.enableCors({
+    origin: /^https:\/\/([a-z0-9-]+\.)?dezky\.local$/,
+    credentials: true,
+  })
+
+  app.useGlobalPipes(
+    new ValidationPipe({
+      whitelist: true,
+      forbidNonWhitelisted: true,
+      transform: true,
+      transformOptions: { enableImplicitConversion: true },
+    }),
+  )
+
+  const port = Number(process.env.PORT ?? 3001)
+  await app.listen(port, '0.0.0.0')
+
+  console.log(`platform-api listening on http://0.0.0.0:${port}`)
+}
+
+bootstrap().catch((err) => {
+  console.error('Failed to start platform-api', err)
+  process.exit(1)
+})