v0.4.40

Release 0.4.40

• README: Add Gemini 2.5 Flash Image docs (text-to-image, edit, fusion), aliases, return_images usage, availability notes
• Version bump to 0.4.40 in pyproject.toml, setup.py, src/init.py
• PyPI: https://pypi.org/project/ai-proxy-core/0.4.40/
• PR #34: #34

Link to Devin run: https://app.devin.ai/sessions/ac6ad5798ea7497ba0758163a0425b10
Requested by: Elijah Arbee (@ebowwa)