Reorganize to dedicated namespaces with automatic cleanup

**Namespace Structure:**
- neonvortex: Application deployment and webhook listener
- flux-builds: Build jobs with automatic cleanup
- flux-system: Flux CD control plane (unchanged)

**Automatic Cleanup:**
- Build jobs: 30-minute TTL after completion
- Cleanup CronJob: Runs every 30 minutes
  - Keeps last 10 successful builds
  - Deletes failed jobs older than 1 hour
  - Removes all jobs older than 24 hours

**Changes:**
- Moved HelmRelease from default to neonvortex namespace
- Moved build jobs from default to flux-builds namespace
- Updated webhook listener to create jobs in flux-builds
- Updated Flux alerts to monitor new namespace
- Cleaned up all resources from default namespace
- Added dedicated ServiceAccounts and RBAC per namespace

**Benefits:**
- Clean namespace separation for better organization
- Automatic job cleanup prevents resource accumulation
- Build history maintained (last 10 successful builds)
- Improved monitoring and troubleshooting
- Default namespace is now clean

Comprehensive migration guide in NAMESPACE_MIGRATION_GUIDE.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

namespaces.yaml

@@ -0,0 +1,16 @@
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: neonvortex
+  labels:
+    app: neonvortex
+    toolkit.fluxcd.io/tenant: neonvortex
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: flux-builds
+  labels:
+    app: flux-builds
+    toolkit.fluxcd.io/tenant: neonvortex