feat(genai): Update google-genai SDK for improvements

[Prajna1999]

Issue

Closes #1238

Summary

1. Updated google-genai SDK to ">=2.25.0" for google-aistudio flow.
2. Update from GenerateContent to Interaction API as the primary mode of making calls to gemini.
3. Update default TTS model to gemini-3.8-flash-tts as the older model gemini-3.1-flash-tts-preview is going to be deprecated from 17th November.
4. Removed deprecated parameters i.e temperature; updated thinking levels.
5. Removed code duplication from gcp and aistudio flow.

Checklist

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• Ran fastapi run --reload app/main.py or docker compose up in the repository root and test.
• If you've fixed a bug or added code that is tested and has test cases.

Notes

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Original PR description

Issue

Closes #PLEASE_TYPE_ISSUE_NUMBER

Summary

Explain the motivation for making this change. What existing problem does the pull request solve?

Checklist

Before submitting a pull request, please ensure that you mark these task.

• Ran fastapi run --reload app/main.py or docker compose up in the repository root and test.
• If you've fixed a bug or added code that is tested and has test cases.

Notes

Please add here if any other information is required for the reviewer.

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[github-actions]

OpenAPI changes   🟢 8 non-breaking changes

Tip

Safe to merge from an API-contract perspective.

Full changelog  ·  8

	Method	Path	Change
🟢	POST	/api/v1/configs	the model request property default value changed from gemini-3.1-flash-tts-preview to gemini-3.8-flash-tts
🟢	POST	/api/v1/configs	added the new minimal enum value to the request property config_blob/completion/anyOf[subschema #2: KaapiTextCompletionConfig]/params/thinking_level/anyOf[subschema #1]/
🟢	POST	/api/v1/llm/call	the model request property default value changed from gemini-3.1-flash-tts-preview to gemini-3.8-flash-tts
🟢	POST	/api/v1/llm/call	added the new minimal enum value to the request property config/blob/anyOf[subschema #1: ConfigBlob]/completion/anyOf[subschema #2: KaapiTextCompletionConfig]/params/thinking_level/anyOf[subschema #1]/
🟢	POST	/api/v1/llm/chain	the model request property default value changed from gemini-3.1-flash-tts-preview to gemini-3.8-flash-tts
🟢	POST	/api/v1/llm/chain	added the new minimal enum value to the request property blocks/items/config/blob/anyOf[subschema #1: ConfigBlob]/completion/anyOf[subschema #2: KaapiTextCompletionConfig]/params/thinking_level/anyOf[subschema #1]/
🟢	POST	/api/v1/llm/chain/sts	the model request property default value changed from gemini-3.1-flash-tts-preview to gemini-3.8-flash-tts
🟢	POST	/api/v1/llm/chain/sts	added the new minimal enum value to the request property rag/anyOf[subschema #1: RAGBlockSpec]/params/anyOf[subschema #1: TextLLMParams]/thinking_level/anyOf[subschema #1]/

_{main ↔ 2e9e9605 · generated by oasdiff}

[codecov]

Codecov Report

❌ Patch coverage is 99.65517% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...kend/app/services/llm/providers/google_aistudio.py	98.29%	2 Missing ⚠️

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