chore(deps): bump google-generativeai from 0.5.4 to 0.7.2 in /backend

Bumps [google-generativeai](https://github.com/google/generative-ai-python) from 0.5.4 to 0.7.2.
- [Release notes](https://github.com/google/generative-ai-python/releases)
- [Changelog](https://github.com/google-gemini/generative-ai-python/blob/main/RELEASE.md)
- [Commits](https://github.com/google/generative-ai-python/compare/v0.5.4...v0.7.2)

---
updated-dependencies:
- dependency-name: google-generativeai
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

@@ -30,7 +30,7 @@ APScheduler==3.10.4
 # AI libraries
 openai
 anthropic
-google-generativeai==0.5.4
+google-generativeai==0.7.2
 tiktoken
 
 langchain==0.2.6