Replace httpretty with requests-mock, update runtimes and add type annotations

[rkoopmans]

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[Copilot]

Pull Request Overview

This pull request updates the test suite to replace HTTPretty with requests-mock and adjusts the supported runtimes. Key changes include converting tests from unittest to pytest style, revising mocking handlers and fixtures accordingly, and updating runtime support (dropping Python 3.7 and adding Python 3.12/3.13).

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/conftest.py	Introduces new pytest fixtures including dummy_file and reset_tinify fixtures; adds a mock_requests fixture using requests-mock.
test/integration.py	Refactors integration tests to pytest-style functions and updates assertions.
test/tinify_test.py	Converts tests from HTTPretty-based mocking to using requests-mock; updates client and app identifier tests.
test/tinify_result_meta_test.py	Updates meta tests to use pytest fixtures and assertions.
test/tinify_result_test.py	Rewrites result tests in pytest style with streamlined assertions.
setup.py	Updates installation and test dependencies; revises package metadata and classifiers.
CHANGES.md	Documents runtime support changes and the switch from HTTPretty to requests-mock.
.github/workflows/ci-cd.yml	Adjusts the testing matrix to match the new runtime support.
test/tinify_source_test.py	Refactors source tests to pytest style; updates mocking logic and helper functions.
tinify/version.py	Bumps the version to 1.6.1.
test/helper.py	Removes deprecated helper methods previously based on HTTPretty.

Comments suppressed due to low confidence (2)

setup.py:40

• The classifiers still list Python 2.7 even though the changelog indicates dropping Python 3.7; please verify the intended supported Python versions and update the classifiers accordingly to avoid confusion.

"Programming Language :: Python :: 2.7",

test/tinify_source_test.py:11

• [nitpick] Consider removing this duplicate helper function if a shared version exists in the conftest.py to reduce code duplication and maintain a single source of truth for temporary file creation.

def create_named_tmpfile():