fix: phase 0 quick wins — safety, naming, and portability

- Add helm.sh/resource-policy: keep to PVC (prevent data loss on uninstall)
- Add fail guard for empty name value in Helm templates
- Fix Makefile IMAGE_NAME from antigravity to devcontainer
- Pin busybox:1.37, homeassistant:v6.7.1, playwright:v0.0.68 (was latest/stable)
- Set imagePullPolicy: IfNotPresent on pinned sidecars
- Remove fetch/sequentialthinking from .mcp.json (sidecars removed from chart)
- Default storage.className to empty (use cluster default, was ceph-filesystem)
- Default Happy Coder URLs to empty (was private farh.net endpoints)
- Broaden githubRepo schema to accept GitLab/Gitea URLs
- Add unknown IDE warning before VSCode fallback
- Add mkdir -p before credential file write (fix fresh PVC boot)
- Guard app user existence in cont-init-user.sh
- Add NOTES.txt post-install template with port-forward and secret hints
- Add standard app.kubernetes.io/* labels and separate selectorLabels

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

chart/values.schema.json

@@ -35,7 +35,7 @@
     "githubRepo": {
       "type": "string",
       "description": "GitHub repository URL to clone",
-      "pattern": "^https://github\\.com/.+/.+$"
+      "pattern": "^https?://.+/.+/.+$"
     },
     "ide": {
       "type": "object",
@@ -108,7 +108,7 @@
           "description": "Storage class name (must support ReadWriteMany)"
         }
       },
-      "required": ["size", "className"]
+      "required": ["size"]
     },
     "resources": {
       "type": "object",
@@ -143,12 +143,10 @@
       "properties": {
         "serverUrl": {
           "type": "string",
-          "format": "uri",
           "description": "Happy Coder server URL"
         },
         "webappUrl": {
           "type": "string",
-          "format": "uri",
           "description": "Happy Coder webapp URL"
         },
         "homeDir": {
@@ -161,7 +159,7 @@
           "description": "Enable experimental Happy features"
         }
       },
-      "required": ["serverUrl", "webappUrl", "homeDir", "experimental"]
+      "required": ["homeDir", "experimental"]
     },
     "mcp": {
       "type": "object",