refactor: update Dockerfile and authentication flow for improved user experience

- Updated Dockerfile to create a cache directory for Next.js runtime, ensuring proper permissions and ownership.
- Enhanced the authentication flow by updating the magic link expiration time from 5 to 15 minutes, improving user experience and reducing login issues.
- Added user-friendly error handling for invalid or expired magic links, providing clear feedback on the login page.
- Adjusted email templates to reflect the new 15-minute validity period for magic links.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.claude/settings.json

@@ -1,7 +1,7 @@
 {
   "enabledPlugins": {
-    "superpowers@superpowers-marketplace": true,
-    "prd-development@pm-skills": true
+    "superpowers@superpowers-marketplace": false,
+    "prd-development@pm-skills": false
   },
   "extraKnownMarketplaces": {
     "superpowers-marketplace": {