feat: add GEMINI_API_KEY and Pollinations.ai fallbacks for image generation

[nadimtuhin]

Problem

Users hit ImageGenerationBlocked when the image-gen SIDCC rotates out of Chrome's SQLite store between uses. Currently there's no way to generate images in that window without a manual cookie refresh.

Solution

Two optional fallback backends, both opt-in via env vars so existing users are completely unaffected:

1. Google AI Studio API key (GEMINI_API_KEY)

export GEMINI_API_KEY=AIzaSy...   # from aistudio.google.com/apikey

Uses the official generativelanguage.googleapis.com endpoint. Tried first when the env var is present; falls back to the cookie session on 429 or error. Supports an optional model override:

export GEMINI_IMAGE_API_MODEL=gemini-2.5-flash-image   # default

2. Pollinations.ai (GEMINI_USE_POLLINATIONS=1)

export GEMINI_USE_POLLINATIONS=1

Zero-auth, no-account-required image generation via Pollinations.ai (free, MIT-licenced service). Uses curl_cffi Chrome impersonation — plain urllib gets a 403. Generates images using the Flux model.

Behaviour

Both paths are attempted only for simple text-to-image requests (prompt only, no files, no conversation_id). Editing, chat, and file-upload flows are completely unchanged.

Priority order when both are configured:

1. GEMINI_API_KEY — official API, highest quality
2. GEMINI_USE_POLLINATIONS=1 — zero-auth fallback
3. Browser cookie session — existing behaviour

Testing

# Test API key path
export GEMINI_API_KEY=<your-key>
# Ask Claude: "generate an image of a red circle"

# Test Pollinations path
export GEMINI_USE_POLLINATIONS=1
# Ask Claude: "generate an image of a red circle"
# Works even without GEMINI_PSID set

Checklist

• Opt-in only — no behaviour change for existing users
• Both paths short-circuit before the library session is initialised
• PermissionError handled gracefully in path checks
• No new required dependencies (curl_cffi already in the dependency tree)
• Env vars documented in commit message

🤖 Generated with Claude Code