feat: thunar & papirus-folders theming + new schemes (#80)

* feat: GTK app theming system

- Implemented custom.css import for user-managed app themes
- process_app_themes() to dynamically update colors in imported CSS files
- Inline comment markers for color replacement (e.g, /* accent-color */)
- Papirus icon color syncing with weighted hue/saturation algorithm

This allows users to create modular app themes that automatically update when the scheme/wallpaper changes

Example usage:
  .app .element { color: #24BD5C; /* accent-color */ }
  .app .element:hover { background: rgba(36, 189, 92, 0.15); /* accent-color with 15% opacity */ }

* feat: atomic theme changes with locking and mode-specific CSS

- Implemented locking to prevent concurrent theme changes
- Added mode-light/mode-dark CSS markers for dynamic property reordering
- Made terminal writes and Papirus sync non-blocking to prevent hangs
- Only save scheme.json after successful theme application

Fixes race conditions during rapid theme switching and ensures Shell and GTK apps scheme stay in sync.

* theme: added to color mapping for custom theming, new schemes

* theme: quick fixes, cleanup

* theme: include thunar.css as template, with new theming system

* theme: modified GTK theming approach

- Dropped comment targeted theming in favor for existing {{  }} replacement
- [app].css.template file created for customization, bypassing built in default if present
- Handling *.template for added templates to be parsed and added to import

* theme: fixes for  thunar.css

* theme: remove .template file use

* theme: path button color adjustment, non-active hover

* fixes & cleanup

* thunar css fixes

* more css fixes

* format

* fix tab vert spacing

---------

Co-authored-by: 2 * r + 2 * t <61896496+soramanew@users.noreply.github.com>

src/caelestia/data/schemes/solarized/medium/dark.txt

@@ -0,0 +1,110 @@
+primary_paletteKeyColor 268BD2
+secondary_paletteKeyColor 2AA198
+tertiary_paletteKeyColor 6C71C4
+neutral_paletteKeyColor 002B36
+neutral_variant_paletteKeyColor 073642
+background 002B36
+onBackground FDF6E3
+surface 073642
+surfaceDim 001F29
+surfaceBright 0D4250
+surfaceContainerLowest 00151D
+surfaceContainerLow 0A404E
+surfaceContainer 094B59
+surfaceContainerHigh 0D4250
+surfaceContainerHighest 11505E
+onSurface FDF6E3
+surfaceVariant 094B59
+onSurfaceVariant 93A1A1
+inverseSurface FDF6E3
+inverseOnSurface 002B36
+outline 586E75
+outlineVariant 0D4250
+shadow 000000
+scrim 000000
+surfaceTint 268BD2
+primary 268BD2
+onPrimary 002B36
+primaryContainer 0D4250
+onPrimaryContainer 268BD2
+inversePrimary 2075B2
+secondary 2AA198
+onSecondary 002B36
+secondaryContainer 0D4250
+onSecondaryContainer 2AA198
+tertiary 6C71C4
+onTertiary 002B36
+tertiaryContainer 0D4250
+onTertiaryContainer 6C71C4
+error DC322F
+onError 002B36
+errorContainer 4C3743
+onErrorContainer DC322F
+primaryFixed 268BD2
+primaryFixedDim 2075B2
+onPrimaryFixed 002B36
+onPrimaryFixedVariant 094B59
+secondaryFixed 2AA198
+secondaryFixedDim 228178
+onSecondaryFixed 002B36
+onSecondaryFixedVariant 094B59
+tertiaryFixed 6C71C4
+tertiaryFixedDim 5C61A4
+onTertiaryFixed 002B36
+onTertiaryFixedVariant 094B59
+term0 002B36
+term1 DC322F
+term2 859900
+term3 B58900
+term4 268BD2
+term5 D33682
+term6 2AA198
+term7 EEE8D5
+term8 586E75
+term9 CB4B16
+term10 859900
+term11 B58900
+term12 268BD2
+term13 6C71C4
+term14 2AA198
+term15 FDF6E3
+rosewater FDF6E3
+flamingo EEE8D5
+pink D33682
+mauve 6C71C4
+red DC322F
+maroon CB4B16
+peach CB4B16
+yellow B58900
+green 859900
+teal 2AA198
+sky 2AA198
+sapphire 268BD2
+blue 268BD2
+lavender 6C71C4
+klink 268BD2
+klinkSelection 268BD2
+kvisited 6C71C4
+kvisitedSelection 6C71C4
+knegative DC322F
+knegativeSelection DC322F
+kneutral B58900
+kneutralSelection B58900
+kpositive 859900
+kpositiveSelection 859900
+text FDF6E3
+subtext1 93A1A1
+subtext0 839496
+overlay2 657B83
+overlay1 586E75
+overlay0 073642
+surface2 094B59
+surface1 073642
+surface0 002B36
+base 002B36
+mantle 001F29
+crust 00151D
+success 859900
+onSuccess 002B36
+successContainer 0D4250
+onSuccessContainer FDF6E3