feat: add Drone CI pipelines, Jest unit tests, and Prettier check

Add Drone CI with server build/test and format check pipelines.
Add unit tests for password utils and recurrenceExpander.
Add check_format script, fix Jest config to ignore dist/,
remove dead CaldavService.test.ts, apply Prettier formatting.

package.json

@@ -7,7 +7,8 @@
     "packages/*"
   ],
   "scripts": {
-    "format": "prettier --write \"apps/*/src/**/*.{ts,tsx}\" \"packages/*/src/**/*.ts\""
+    "format": "prettier --write \"apps/*/src/**/*.{ts,tsx}\" \"packages/*/src/**/*.ts\"",
+    "check_format": "prettier --check \"apps/*/src/**/*.{ts,tsx}\" \"packages/*/src/**/*.ts\""
   },
   "devDependencies": {
     "eslint": "^9.25.0",