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/llm_gateway/models/__init__.py

@@ -0,0 +1,31 @@
+"""
+Pydantic Models für OpenAI-kompatible API.
+"""
+
+from .chat import (
+    ChatMessage,
+    ChatCompletionRequest,
+    ChatCompletionResponse,
+    ChatCompletionChunk,
+    ChatChoice,
+    ChatChoiceDelta,
+    Usage,
+    ToolCall,
+    FunctionCall,
+    Tool,
+    ToolFunction,
+)
+
+__all__ = [
+    "ChatMessage",
+    "ChatCompletionRequest",
+    "ChatCompletionResponse",
+    "ChatCompletionChunk",
+    "ChatChoice",
+    "ChatChoiceDelta",
+    "Usage",
+    "ToolCall",
+    "FunctionCall",
+    "Tool",
+    "ToolFunction",
+]