release: v0.4 – import, backup ZIP, account self-service, repeating tasks

- Import of MindSift data (add or restore) and Obsidian vaults, backup as ZIP
- Danger zone (delete own data / account), last admin protected
- Repeating tasks, SMTP AUTH LOGIN fallback and port fix
- Mobile: sheets above the keyboard, emoji picker fixes, blue splash screen
- Package version 0.4.0, README badge/screenshots renewed

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "mindsift-frontend",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "mindsift-frontend",
-      "version": "0.3.0",
+      "version": "0.4.0",
       "dependencies": {
         "@types/prismjs": "^1.26.6",
         "emoji-picker-react": "^4.12.0",