fix: Restore all files lost during destructive rebase

A previous `git pull --rebase origin main` dropped 177 local commits,
losing 3400+ files across admin-v2, backend, studio-v2, website,
klausur-service, and many other services. The partial restore attempt
(660295e2) only recovered some files.

This commit restores all missing files from pre-rebase ref 98933f5e
while preserving post-rebase additions (night-scheduler, night-mode UI,
NightModeWidget dashboard integration).

Restored features include:
- AI Module Sidebar (FAB), OCR Labeling, OCR Compare
- GPU Dashboard, RAG Pipeline, Magic Help
- Klausur-Korrektur (8 files), Abitur-Archiv (5+ files)
- Companion, Zeugnisse-Crawler, Screen Flow
- Full backend, studio-v2, website, klausur-service
- All compliance SDKs, agent-core, voice-service
- CI/CD configs, documentation, scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

klausur-service/backend/models/exam.py

@@ -0,0 +1,68 @@
+"""
+Klausur-Service Exam Models
+
+Data classes for Klausur and StudentKlausur.
+"""
+
+from dataclasses import dataclass, asdict
+from datetime import datetime
+from typing import Optional, List, Dict, Any
+
+from .enums import KlausurModus, StudentKlausurStatus
+
+
+@dataclass
+class StudentKlausur:
+    """A student's exam work."""
+    id: str
+    klausur_id: str
+    student_name: str
+    student_id: Optional[str]
+    file_path: Optional[str]
+    ocr_text: Optional[str]
+    status: StudentKlausurStatus
+    criteria_scores: Dict[str, Dict]
+    gutachten: Optional[Dict]
+    raw_points: int
+    grade_points: int
+    created_at: datetime
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Convert to dictionary for JSON serialization."""
+        d = asdict(self)
+        d['status'] = self.status.value if hasattr(self.status, 'value') else self.status
+        d['created_at'] = self.created_at.isoformat()
+        return d
+
+
+@dataclass
+class Klausur:
+    """An exam/Klausur with associated student works."""
+    id: str
+    title: str
+    subject: str
+    modus: KlausurModus
+    class_id: Optional[str]
+    year: int
+    semester: str
+    erwartungshorizont: Optional[Dict]
+    students: List[StudentKlausur]
+    created_at: datetime
+    teacher_id: str
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Convert to dictionary for JSON serialization."""
+        return {
+            'id': self.id,
+            'title': self.title,
+            'subject': self.subject,
+            'modus': self.modus.value,
+            'class_id': self.class_id,
+            'year': self.year,
+            'semester': self.semester,
+            'erwartungshorizont': self.erwartungshorizont,
+            'student_count': len(self.students),
+            'students': [s.to_dict() for s in self.students],
+            'created_at': self.created_at.isoformat(),
+            'teacher_id': self.teacher_id
+        }