feat: Add comprehensive backend validation, toast notifications, and Tokyo Night theme

- Backend: Add server-side validation with go-playground/validator/v10
- Frontend: Add toast notifications for API errors with @zerodevx/svelte-toast
- UI: Complete Tokyo Night theme redesign with modern animations
- Docs: Update COMPLETE_DOCUMENTATION.md and README.md with all enhancements
- Validation: Email format, password strength, and input sanitization
- UX: Real-time error feedback, loading states, and responsive design

bruno/auth/Get Profile.yml

@@ -0,0 +1,23 @@
+meta:
+  name: Get Profile
+  seq: 3
+http:
+  method: get
+  url: "{{base_url}}/api/auth/profile"
+  auth:
+    type: bearer
+docs: |
+  ## Get User Profile
+
+  Retrieves the profile of the authenticated user.
+
+  **Authentication:** Required (Bearer token)
+
+  **Response:**
+  - `id` (string): User UUID
+  - `email` (string): User's email address
+  - `username` (string): User's username
+
+  **Error Responses:**
+  - 401: Invalid or missing JWT token
+  - 404: User not found