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/alembic/env.py

@@ -0,0 +1,107 @@
+"""
+Alembic Environment Configuration fuer Classroom Engine.
+
+Laedt die DB-Konfiguration und Models fuer Migrationen.
+"""
+import os
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# Alembic Config
+config = context.config
+
+# Logging Setup
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# Import unserer Models fuer autogenerate
+from classroom_engine.database import Base
+from classroom_engine.db_models import (
+    LessonSessionDB,
+    PhaseHistoryDB,
+    TeacherSettingsDB,
+)
+
+# Alerts Agent Models (nutzt gleiche Base)
+from alerts_agent.db.models import (
+    AlertTopicDB,
+    AlertItemDB,
+    AlertRuleDB,
+    AlertProfileDB,
+)
+
+# Test Registry Models
+try:
+    from api.tests.db_models import (
+        TestRunDB,
+        TestResultDB,
+        FailedTestBacklogDB,
+        TestFixHistoryDB,
+        TestServiceStatsDB,
+    )
+except ImportError:
+    # Models noch nicht vorhanden - wird bei Migration erstellt
+    pass
+
+target_metadata = Base.metadata
+
+# Database URL aus Umgebungsvariable oder Config
+_raw_url = os.getenv(
+    "DATABASE_URL",
+    config.get_main_option("sqlalchemy.url")
+)
+# SQLAlchemy 2.0 erfordert "postgresql://" statt "postgres://"
+DATABASE_URL = _raw_url.replace("postgres://", "postgresql://", 1) if _raw_url and _raw_url.startswith("postgres://") else _raw_url
+
+
+def run_migrations_offline() -> None:
+    """
+    Run migrations in 'offline' mode.
+
+    Generiert SQL-Skripte ohne DB-Verbindung.
+    """
+    url = DATABASE_URL
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """
+    Run migrations in 'online' mode.
+
+    Fuehrt Migrationen direkt auf der DB aus.
+    """
+    configuration = config.get_section(config.config_ini_section)
+    configuration["sqlalchemy.url"] = DATABASE_URL
+
+    connectable = engine_from_config(
+        configuration,
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()