Add Python 3.14 support to workflows and metadata

[EwoutH]

Updated GitHub Actions workflows to use Python 3.14 and added Python 3.14 classifier to pyproject.toml for official support.

[EwoutH]

Blocked by an upstream issue at Solara: widgetti/solara#1107.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
BoltzmannWealth	small	🔵 -0.6% [-1.2%, -0.1%]	🔵 -0.1% [-0.2%, +0.1%]
BoltzmannWealth	large	🔵 -1.0% [-2.6%, -0.0%]	🔵 +1.2% [+0.5%, +2.1%]
Schelling	small	🔵 -0.1% [-0.3%, +0.1%]	🔵 -0.1% [-0.3%, +0.0%]
Schelling	large	🔵 +0.1% [-0.1%, +0.4%]	🔵 -2.1% [-3.0%, -1.3%]
WolfSheep	small	🔵 -1.4% [-1.6%, -1.2%]	🔵 +1.4% [+1.2%, +1.5%]
WolfSheep	large	🔵 -0.6% [-0.9%, -0.3%]	🔵 -0.4% [-1.3%, +0.3%]
BoidFlockers	small	🔵 +0.3% [-0.2%, +0.8%]	🔵 -0.7% [-0.9%, -0.6%]
BoidFlockers	large	🔵 +0.4% [+0.0%, +0.8%]	🔵 -0.9% [-1.1%, -0.7%]