Drop Python 3.9 support across DataLab and generated plugins #423

Context

The workspace is retiring Python 3.9 support. GitHub Actions ubuntu-latest is moving to Ubuntu 26.04, for which actions/setup-python does not provide CPython 3.9 builds. CPython 3.10 builds are available.

Scope

Raise the minimum, classifiers, Ruff target and both Qt CI boundaries to 3.10; update generated plugin projects and Desktop catalog targets; remove exclusively 3.9 entry-point/resource/wheel fallbacks with regression tests; update live/generated/French documentation and release notes. Exclude 3.9 from current Windows test matrices while retaining explicit historical-release testing; preserve user configuration and Python 3.11 standalone builds.

Delivery and acceptance

• Target branch: develop.
• One dedicated PR for this repository, linked to this issue; preserve unrelated changes and published historical artifacts.
• Validate changed behavior and metadata on the retained runtimes; report exact results and unavailable checks.
• Keep ubuntu-latest; do not globally upgrade dependency bounds or add Python 3.15 support.
• Merge only after applicable checks pass on the current PR head and branch protections are satisfied. Where no PR CI exists (Camera, Pulse and platform docs), documented local validation is the explicitly approved gate.
• Close this issue only after the corresponding PR is verified as merged. No package release or promotion to another stable branch is authorized by this task.