Add port-aware auto presets

[bhack]

Summary

• add port-aware auto presets backed by pipewire-gobject device route params
• simplify output selection around device-first labels with a visible output/port scope row
• refresh preset actions around neutral reset, bounded imported APO curve state, overwrite confirmation, and auto preset defaults
• update deterministic release screenshots and social preview
• align GNOME Shell extension wording with the app auto-preset terminology

Validation

• ruff check .
• ruff format --check .
• pytest -q
• MINI_EQ_RUN_ATSPI=1 pytest tests/test_mini_eq_atspi_widgets.py -q
• appstreamcli validate --no-net data/io.github.bhack.mini-eq.metainfo.xml
• desktop-file-validate data/io.github.bhack.mini-eq.desktop
• tools/check_gnome_shell_extension.py --no-package
• local pipewire-gobject probe/check-deps against the strict sibling build
• live UI runtime smoke with the local strict pipewire-gobject build
• containerized release preflight using public pipewire-gobject 0.3.5
• vulture, dead-fixtures, test hygiene, and coverage pytest cleanup checks
• installed local Flatpak runtime smoke against io.github.bhack.mini-eq//master
• PR CI is green, including Flatpak build

Remaining release gates

• owner interactive test with real music on the target hardware/output ports
• GNOME Shell extension upload because extension source/metadata changed
• Flathub manifest update after the v0.7.0 release archive and SHA-256 exist