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/progress/Get Reading Progress.yml

@@ -0,0 +1,31 @@
+meta:
+  name: Get Reading Progress
+  seq: 6
+http:
+  method: get
+  url: "{{base_url}}/api/ebooks/{{ebook_id}}/progress"
+  auth:
+    type: bearer
+vars:
+  pre-request:
+    - name: ebook_id
+      value: "123e4567-e89b-12d3-a456-426614174000"
+docs: |
+  ## Get Reading Progress
+
+  Retrieves the authenticated user's reading progress for an ebook.
+
+  **Authentication:** Required (Bearer token)
+
+  **Path Parameters:**
+  - `id` (string): Ebook UUID
+
+  **Response:**
+  - `ebook_id` (string): Ebook UUID
+  - `user_id` (string): User UUID
+  - `current_page` (number): Current page number
+  - `total_pages` (number, nullable): Total pages
+  - `last_read_at` (string): Last read timestamp
+
+  **Error Responses:**
+  - 401: Invalid authentication