Fixes #187 : Correct Gemini API Model for generateContent

[ragingtitan]

Description

This PR fixes a critical bug where the Gemini API call fails due to an unsupported model name (gemini-2.5-flash-preview-04-17).
As a result, the “Discover Fact” feature was unable to generate content, even with a valid API key.

The fix ensures that the app now uses a valid, supported Gemini model (gemini-2.5-flash-preview-05-20) for text generation.

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Changes Made

• Updated GEMINI_MODEL_TEXT_GENERATION constant to use a supported model.
• Replaced deprecated/unsupported model reference across:
  • services/geminiService.ts
  • constants.ts
• Verified compatibility with the generateContent method of the Gemini API.

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Issue Reference

Closes #187

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Steps to Test

1. Pull this branch.
2. Ensure process.env.API_KEY is set to a valid Gemini API key.
3. Navigate to the Giveaways page.
4. Click “Discover Fact”.
5. Confirm that:
   • No 404 error appears in the console.
   • A valid tech fact is generated and displayed successfully.

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Before vs After

Before:
404 NOT_FOUND error due to gemini-2.5-flash-preview-04-17.

After:
Tech fact generated successfully with gemini-2.5-flash-preview-05-20.

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Labels

• bug
• fix
• gssoc25
• level 3

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Notes

Ensuring the correct Gemini model restores the Discover Fact functionality and prevents API call failures in both development and production.

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