Add Python 3.14 support, drop 3.9, modernize CI infrastructure

[Copilot]

Updates Python version matrix and modernizes build infrastructure across all platforms.

Python

• Add 3.14, remove 3.9 (EOL)
• Use numpy 2.3.* for 3.14 (first version with cp314 wheels)

CI Runners

• macOS: macos-13 → macos-15-intel, macos-14 → macos-15
• Windows: windows-2019 → windows-2025

macOS Build

• Min deployment target: 13.0 → 14.0
• libffi: 3.4.3 → 3.5.2
• Add libpcre2 10.45 (glib dependency, 8-bit only)

Build Scripts

• Upgrade pip, set PIP_PREFER_BINARY=1 (all platforms)
• Linux: dynamic Python path detection:

  PYVER_NO_DOT=${PYTHON_VERSION//./}
  PYBIN="/opt/python/cp${PYVER_NO_DOT}-cp${PYVER_NO_DOT}/bin"

• Windows: prefer newest VS version (2022 → 2019 → 2017)

Workflow

• Add concurrency to cancel in-progress runs on new pushes

Dependencies

• lensfun: v0.3.3 → v0.3.4

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