Add Pydantic v1/v2 compatibility for Input validators

[patrick91]

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[github-actions]

Thanks for adding the RELEASE.md file!

Below is the changelog that will be used for the release.

---

Add Pydantic v1/v2 compatibility for Input validators using a Protocol-based approach.

The Input component now accepts any object with a validate_python method through the new Validator protocol, making it compatible with both Pydantic v1 and v2.

Usage with Pydantic v2:

from pydantic import TypeAdapter

validator = TypeAdapter(int)
app.input("Enter a number:", validator=validator)

Usage with Pydantic v1:

from pydantic import parse_obj_as

class V1Validator:
    def __init__(self, type_):
        self.type_ = type_

    def validate_python(self, value):
        return parse_obj_as(self.type_, value)

validator = V1Validator(int)
app.input("Enter a number:", validator=validator)

Changes:

• Added Validator protocol that accepts any object with a validate_python method
• Improved error message extraction from Pydantic validation errors
• Added cross-version compatibility tests
• Updated CI to test both Pydantic v1 and v2 across Python 3.8-3.14

This release was contributed by @patrick91 in #39

[github-actions]

This PR was published as 0.16.0