docs: update README to clarify changes in PyPI versioning for Fish Audio Python SDK

[twangodev]

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[codecov-commenter]

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[Copilot]

Pull Request Overview

This PR updates the README documentation to inform users about a significant change in the PyPI versioning scheme for the Fish Audio Python SDK. The versioning is being reset from 2025.6.3 to 1.0.0, requiring users to update their dependency constraints to continue receiving updates.

• Adds a prominent "Important" notice explaining the versioning reset from 2025.6.3 to 1.0.0
• Provides clear instructions for users to update their dependency constraints
• Distinguishes between the versioning change (no API changes) and the legacy API migration

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[Copilot]

The phrase "on Fish Audio Python SDK" is grammatically awkward. Consider revising to "of the Fish Audio Python SDK" or "using the Fish Audio Python SDK" for better clarity and readability.

Suggested change

	> For existing users on Fish Audio Python SDK, please note that the starting version is now `1.0.0`. The last version before this was `2025.6.3`. You may need to adjust your version constraints accordingly.
	> For existing users of the Fish Audio Python SDK, please note that the starting version is now `1.0.0`. The last version before this was `2025.6.3`. You may need to adjust your version constraints accordingly.