feat: Implement API modules for admin, auth, exam, result, and setup functionalities

- Created adminApi.ts for admin-related operations including user management and site settings.
- Developed authApi.ts for authentication processes such as registration, login, and profile management.
- Added examApi.ts for handling exam CRUD operations.
- Introduced resultApi.ts for managing results submission and retrieval.
- Established setupApi.ts for initial setup processes and status checks.
- Created ErrorBoundary component to handle rendering errors gracefully in the frontend.
- Re-exported shared API utilities in index.ts for easier access.

backend/src/validators/resultSchemas.ts

@@ -0,0 +1,40 @@
+import { z } from 'zod'
+
+const answerValueSchema = z.union([z.string(), z.array(z.string()), z.record(z.string(), z.string())])
+
+export const submitResultSchema = z.object({
+  exam_id: z.number().nullable().optional(),
+  title: z.string().min(1),
+  score_points: z.number(),
+  total_points: z.number(),
+  correct_count: z.number(),
+  graded_count: z.number(),
+  passing_score: z.number().optional(),
+  elapsed_ms: z.number(),
+  state: z.object({
+    answers: z.record(z.string(), answerValueSchema),
+    gradedAnswers: z.record(z.string(), z.object({
+      correct: z.boolean(),
+      points: z.number(),
+      explanation: z.string().optional(),
+    })),
+    answeredCount: z.number(),
+    score: z.number(),
+    correctCount: z.number(),
+    gradedCount: z.number(),
+    timeExpired: z.boolean().optional(),
+  }),
+  exam: z.object({
+    id: z.string().optional(),
+    title: z.string(),
+    subtitle: z.string().optional(),
+    questions: z.array(z.any()),
+    timeLimitMinutes: z.number().nullable().optional(),
+    passingScore: z.number().optional(),
+    feedbackMode: z.enum(['end', 'immediate']).optional(),
+  }).passthrough(),
+})
+
+export const resultIdParamSchema = z.object({
+  id: z.string().regex(/^\d+$/, 'ID must be a number'),
+})