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/ts-algebra/lib/utils/merge.d.ts

@@ -0,0 +1,7 @@
+import type { IsArray, IsObject } from "./extends";
+export declare type DeepMergeUnsafe<TYPE_A, TYPE_B> = IsObject<TYPE_A> extends true ? IsObject<TYPE_B> extends true ? {
+    [KEY in keyof (TYPE_A & TYPE_B)]: KEY extends keyof TYPE_B ? KEY extends keyof TYPE_A ? DeepMergeUnsafe<TYPE_A[KEY], TYPE_B[KEY]> : TYPE_B[KEY] : KEY extends keyof TYPE_A ? TYPE_A[KEY] : never;
+} : TYPE_B : IsArray<TYPE_A> extends true ? IsArray<TYPE_B> extends true ? TYPE_B extends unknown[] ? [
+    ...(TYPE_A extends unknown[] ? TYPE_A : never),
+    TYPE_B
+] : never : TYPE_B : TYPE_B;