feat: Reinitialize frontend with SvelteKit and TypeScript

- Delete old Vite+Svelte frontend
- Initialize new SvelteKit project with TypeScript
- Configure Tailwind CSS v4 + DaisyUI
- Implement JWT authentication with auto-refresh
- Create login page with form validation (Zod)
- Add protected route guards
- Update Docker configuration for single-stage build
- Add E2E tests with Playwright (6/11 passing)
- Fix Svelte 5 reactivity with $state() runes

Known issues:
- 5 E2E tests failing (timing/async issues)
- Token refresh implementation needs debugging
- Validation error display timing

frontend/node_modules/dayjs/esm/plugin/weekday/index.d.ts

@@ -0,0 +1,12 @@
+import { PluginFunc } from 'dayjs/esm'
+
+declare const plugin: PluginFunc
+export = plugin
+
+declare module 'dayjs/esm' {
+  interface Dayjs {
+    weekday(): number
+
+    weekday(value: number): Dayjs
+  }
+}

frontend/node_modules/dayjs/esm/plugin/weekday/index.js

@@ -0,0 +1,15 @@
+export default (function (o, c) {
+  var proto = c.prototype;
+
+  proto.weekday = function (input) {
+    var weekStart = this.$locale().weekStart || 0;
+    var $W = this.$W;
+    var weekday = ($W < weekStart ? $W + 7 : $W) - weekStart;
+
+    if (this.$utils().u(input)) {
+      return weekday;
+    }
+
+    return this.subtract(weekday, 'day').add(input, 'day');
+  };
+});