#169 Linux: symbolic (monochrome) tray icon option

[Anonymous]

Originally created by: kristofferR

The full-color logo looks out of place in GNOME/KDE panels next to symbolic icons. Add an opt-in monochrome tray variant.

• Pixmap-based, not icon-name theme lookup — theme dirs are invisible to the panel process for AppImage installs, and ksni's icon_theme_path is host-dependent. A pixmap behaves identically across deb/rpm/AppImage/AUR/Flatpak.
• New asset src-tauri/icons/tray/carrier-symbolic.png: monochrome white glyph + alpha, derived from the existing mark; embedded via include_bytes!.
• New Linux-only setting tray_icon_style: "color" | "symbolic" (default "color"), following the badge_mode pattern (field, default, sanitized() fallback, baked-settings merge, Linux-only Settings row, apply_settings → tray handle update).
• Symbolic mode tints the glyph off the freedesktop color-scheme portal already watched in linux.rs: white on dark, dark gray on light. Panels don't report their own theme, so this is a heuristic — hence opt-in rather than default.
• The unread badge (from the visible-unread issue) draws over whichever base is active.

Depends on the tray badge refactor landing first.

Part of [#171].

[Anonymous]

Originally posted by: kristofferR

Implemented and merged in [#195]: Linux users can select the new symbolic monochrome tray icon, including unread badge rendering. Closing as complete.

[Anonymous]

Ticket changed by: kristofferR

• status: open --> closed