AI-Edit-Ebene via OpenRouter (Gemini Image): Studio-Hintergrund, Retusche, Restaurierung + freier Prompt

- app/ai_edit.py: OpenRouter chat/completions (image in/out), Presets + Prompt, Retry
- bot: AI-Preset-Buttons + Bildunterschrift = freier AI-Prompt; _process refaktoriert
- Freistellen/Upscaling bleiben lokal (originaltreu); AI-Edit fuer generative Edits
- httpx pin, config OPENROUTER_*

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNQ8ghPfzAfsyVYd6HgFb6

requirements.txt

@@ -5,6 +5,7 @@ opencv-contrib-python-headless==4.10.0.84
 numpy==1.26.4
 pillow==10.4.0
 aiohttp==3.10.10
+httpx==0.27.2
 paramiko==3.5.0
 pymatting==1.1.12
 scipy==1.13.1