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>

backend/api/tests/database.py

@@ -0,0 +1,91 @@
+"""
+Database Configuration fuer Test Registry.
+
+PostgreSQL-Anbindung fuer persistente Test-Speicherung.
+Ersetzt die bisherige JSON-basierte Speicherung.
+"""
+import os
+from contextlib import contextmanager
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker, Session, declarative_base
+
+# Eigene Base fuer Test Registry - unabhaengig von anderen Modulen
+# Dies vermeidet Import-Probleme in CI/CD Umgebungen
+Base = declarative_base()
+
+# Database URL from environment (nutzt gleiche DB wie Backend)
+_raw_url = os.getenv(
+    "DATABASE_URL",
+    "postgresql://breakpilot:breakpilot123@postgres:5432/breakpilot_db"
+)
+# SQLAlchemy 2.0 erfordert "postgresql://" statt "postgres://"
+DATABASE_URL = _raw_url.replace("postgres://", "postgresql://", 1) if _raw_url.startswith("postgres://") else _raw_url
+
+# Engine configuration mit Connection Pool
+engine = create_engine(
+    DATABASE_URL,
+    pool_pre_ping=True,  # Prueft Connections vor Nutzung
+    pool_size=5,         # Standard Pool-Groesse
+    max_overflow=10,     # Zusaetzliche Connections bei Bedarf
+    pool_recycle=3600,   # Recycle nach 1 Stunde
+    echo=os.getenv("SQL_ECHO", "false").lower() == "true"
+)
+
+# Session factory
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+def get_db():
+    """
+    Database dependency for FastAPI endpoints.
+    Yields a database session and ensures cleanup.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+@contextmanager
+def get_db_session():
+    """
+    Context manager for database sessions.
+    Use this for background tasks and non-FastAPI code.
+
+    Example:
+        with get_db_session() as db:
+            db.query(TestRun).all()
+    """
+    db = SessionLocal()
+    try:
+        yield db
+        db.commit()
+    except Exception:
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+
+def init_db():
+    """
+    Erstellt alle Tabellen.
+    In Produktion sollte Alembic verwendet werden.
+    """
+    from . import db_models  # Import models to register them
+    Base.metadata.create_all(bind=engine)
+
+
+def check_db_connection() -> bool:
+    """
+    Prueft ob die Datenbankverbindung funktioniert.
+    Nuetzlich fuer Health-Checks.
+    """
+    try:
+        from sqlalchemy import text
+        with get_db_session() as db:
+            db.execute(text("SELECT 1"))
+        return True
+    except Exception:
+        return False