chore: align Python 3.11-3.14 support [CINF-0]

[vkryzh]

What changed

• migrated local development and CI workflows to the uv-based setup carried on this branch
• set Python 3.14 as the default local and CI interpreter
• narrowed the supported SDK/app window to Python 3.11 through 3.14
• updated CI matrix entries, packaging metadata, mypy target version, docs, and lockfile state to match
• documented that Python 3.11 and 3.12 remain supported, but new apps should prefer 3.14

Why it changed

The repository still advertised older Python support and did not consistently describe or exercise the intended runtime window. This change aligns the branch's uv-based workflow with the requested Python support policy and makes 3.14 the default path.

Impact

• local development defaults to Python 3.14
• CI runs against Python 3.11, 3.12, 3.13, and 3.14
• published package metadata now declares >=3.11,<4.0
• SDK consumers still on 3.11 or 3.12 remain supported, but new development is steered toward 3.14

Root cause

The project had stale runtime metadata and docs from older support windows, while this branch already carried uv migration work that needed to be brought into alignment with the new Python 3.11-3.14 policy.

Validation

• make all on Python 3.14
• uv sync --frozen --extra dev --python 3.11
• Python 3.11 smoke import with required settings injected

Notes

This PR includes the existing local uv migration commits already present on the branch (build: migrate to uv and chore: freeze uv commands [CINF-0]) in addition to the runtime-window alignment changes.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Restrict package metadata to supported Python range

This change declares support/testing for Python 3.11–3.14, but requires-python = ">=3.11,<4.0" still permits installation on 3.15+ once those interpreters are available. In that scenario, users can install an explicitly unsupported version and only discover incompatibilities at runtime instead of getting a resolver-time rejection. If the intended support window is truly 3.11–3.14, the upper bound should be capped to <3.15 (and kept consistent with the lockfile).

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