Feature/issue 229 render color profiles

[devmobasa]

Resolves #229

Summary

Implements the remaining Issue #229 render profile workflow without PDF export.

• Adds a Render Profiles configurator tab for creating/editing profiles and mappings.
• Adds active profile, canvas/UI target toggles, and export profile selection.
• Adds explicit canvas PNG export actions for file, clipboard, and clipboard+file.
• Supports export profile modes: off, active profile, or named profile.
• Routes canvas export through the capture delivery path with canvas-specific status/error text.
• Adds keybinding, command palette, help overlay, config docs, and example config wiring.
• Improves Drawing tab configurator performance by rendering one drag-button mapping section at a time.

Notes

• PDF export is intentionally out of scope.
• [capture].enabled still gates screenshot capture only, not explicit canvas export.
• Canvas export writes PNG data and forces PNG extension/clipboard fallback metadata.
• Transparent canvas export remains transparent; it does not include live screen pixels.