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/requirements.txt

@@ -0,0 +1,60 @@
+# BreakPilot Backend Dependencies
+
+# Web Framework
+fastapi==0.123.9
+uvicorn==0.38.0
+starlette==0.49.3
+
+# HTTP Client
+httpx==0.28.1
+requests==2.32.5
+
+# Validation & Types
+pydantic==2.12.5
+pydantic_core==2.41.5
+email-validator==2.3.0
+annotated-types==0.7.0
+
+# Authentication
+PyJWT==2.10.1
+python-multipart==0.0.20
+
+# AI / Anthropic
+anthropic==0.75.0
+
+# Secrets Management
+hvac==2.4.0
+
+# PDF Generation
+weasyprint==66.0
+Jinja2==3.1.6
+
+# Image Processing
+pillow==11.3.0
+opencv-python==4.12.0.88
+numpy==2.0.2
+
+# Document Processing
+python-docx==1.2.0
+mammoth==1.11.0
+Markdown==3.9
+
+# Utilities
+python-dateutil==2.9.0.post0
+
+# Database
+asyncpg==0.30.0
+SQLAlchemy==2.0.36
+psycopg2-binary==2.9.10
+
+# Cache (Valkey/Redis)
+redis==5.2.1
+
+# Testing
+pytest==8.4.2
+pytest-asyncio==1.2.0
+beautifulsoup4==4.12.3
+
+# Security: Pin transitive dependencies to patched versions
+idna>=3.7  # CVE-2024-3651: DoS via resource consumption
+cryptography>=42.0.0  # GHSA-h4gh-qq45-vh27: NULL pointer dereference