feat: integrate AI features for question generation and tutoring

- Added AI routes for generating questions, providing hints, and tutor chat functionality.
- Implemented AI client setup and model retrieval in aiClient.ts.
- Created aiAssist.ts for handling AI-related operations including question generation and hint retrieval.
- Updated services to utilize the new AI client and assist functions.
- Enhanced frontend components to support AI question generation and tutor chat, including UI for generating questions and displaying hints.
- Added localization strings for new AI features in English and Dutch.
- Updated exam review process to include AI-generated hints and tutor chat functionality.

frontend/src/i18n/en.json

@@ -108,7 +108,12 @@
     "flagHint": "flag",
     "selectHint": "select",
     "exit": "Exit",
-    "untimed": "Untimed"
+    "untimed": "Untimed",
+    "needHint": "💡 Need a hint?",
+    "hintLoading": "Thinking…",
+    "hintShown": "💡 Hint shown",
+    "hintTitle": "Get a hint without revealing the answer",
+    "hintLabel": "Hint"
   },
   "results": {
     "ai": {
@@ -120,6 +125,13 @@
       "rubricBreakdown": "Rubric breakdown",
       "error": "AI grading failed — please grade manually"
     },
+    "tutor": {
+      "title": "💬 Ask the tutor",
+      "subtitle": "Ask follow-up questions about this attempt — explanations, similar problems, or rubric details.",
+      "placeholder": "e.g. \"Why was Q2 wrong?\" or \"Give me a similar problem to practice.\"",
+      "inputPlaceholder": "Ask a question…",
+      "send": "Send"
+    },
     "reviewing": "Reviewing past attempt",
     "examComplete": "Exam complete",
     "scored": "You scored ",
@@ -404,7 +416,15 @@
     "choicePlaceholder": "Choice {{id}}",
     "addItem": "+ Add Item",
     "leftItemPlaceholder": "Left item {{index}}",
-    "rightItemPlaceholder": "Right item {{index}}"
+    "rightItemPlaceholder": "Right item {{index}}",
+    "aiGenerate": "✨ Generate with AI",
+    "aiClose": "✕ Close AI",
+    "aiPanelTitle": "Generate questions",
+    "aiTopicPlaceholder": "Topic, e.g. \"Pythagorean theorem\"",
+    "aiContextPlaceholder": "Optional notes or source material to ground the questions in…",
+    "aiGenerateNow": "Generate",
+    "aiGenerating": "Generating…",
+    "aiTopicRequired": "Please enter a topic"
   },
   "setup": {
     "welcome": "Welcome to BrainWave",