feat: drop Python 3.9 support and add Python 3.14 support

[Copilot]

Aligns this SDK with the kiota-python library by removing Python 3.9 support and adding Python 3.14 support.

Changes

• pyproject.toml — bumps requires-python to >=3.10; removes Python :: 3.9 classifier; adds Python :: 3.14 classifier
• .github/workflows/build.yml — removes "3.9" from the CI test matrix; adds "3.14"
• .devcontainer/devcontainer.json — removes the commented-out python:3.9-bookworm image option; updates the active dev container image to python:3.14-bookworm

[ramsessanchez]

@copilot add support for 3.14

[Copilot]

@copilot add support for 3.14

Done in f7193ba. Added "3.14" to the CI matrix in build.yml and the Programming Language :: Python :: 3.14 classifier in pyproject.toml.

[ramsessanchez]

@copilot remove 3.9 from .devcontainer, also make sure target image is 3.14

[Copilot]

@copilot remove 3.9 from .devcontainer, also make sure target image is 3.14

Done in 9c007ec. The 3.9 reference was already removed from a prior commit. The active devcontainer image is now updated to mcr.microsoft.com/devcontainers/python:3.14-bookworm.