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/everblush/medium/dark.txt

@@ -0,0 +1,110 @@
+primary_paletteKeyColor 8CCFB0
+secondary_paletteKeyColor E5C76B
+tertiary_paletteKeyColor E5A5C5
+neutral_paletteKeyColor 2D3139
+neutral_variant_paletteKeyColor 3A3F4B
+background 141B1E
+onBackground E8E8E8
+surface 232A2D
+surfaceDim 0F1416
+surfaceBright 3A4145
+surfaceContainerLowest 0A0E10
+surfaceContainerLow 2A3235
+surfaceContainer 2E3538
+surfaceContainerHigh 3A4145
+surfaceContainerHighest 434A4E
+onSurface E8E8E8
+surfaceVariant 2E3538
+onSurfaceVariant B3B9BE
+inverseSurface E8E8E8
+inverseOnSurface 141B1E
+outline 8A8F94
+outlineVariant 3A4145
+shadow 000000
+scrim 000000
+surfaceTint 8CCFB0
+primary 8CCFB0
+onPrimary 141B1E
+primaryContainer 3A4145
+onPrimaryContainer 8CCFB0
+inversePrimary 6FA98C
+secondary E5C76B
+onSecondary 141B1E
+secondaryContainer 3A4145
+onSecondaryContainer E5C76B
+tertiary E5A5C5
+onTertiary 141B1E
+tertiaryContainer 3A4145
+onTertiaryContainer E5A5C5
+error E57474
+onError 141B1E
+errorContainer 4A2C2C
+onErrorContainer E57474
+primaryFixed 8CCFB0
+primaryFixedDim 6FA98C
+onPrimaryFixed 141B1E
+onPrimaryFixedVariant 3A3F4B
+secondaryFixed E5C76B
+secondaryFixedDim C4A855
+onSecondaryFixed 141B1E
+onSecondaryFixedVariant 3A3F4B
+tertiaryFixed E5A5C5
+tertiaryFixedDim C888A4
+onTertiaryFixed 141B1E
+onTertiaryFixedVariant 3A3F4B
+term0 141B1E
+term1 E57474
+term2 8CCFB0
+term3 E5C76B
+term4 67B0E8
+term5 C47FD5
+term6 6CBFBF
+term7 E8E8E8
+term8 8A8F94
+term9 E57474
+term10 8CCFB0
+term11 E5C76B
+term12 67B0E8
+term13 C47FD5
+term14 6CBFBF
+term15 E8E8E8
+rosewater E8E8E8
+flamingo E5A5C5
+pink E5A5C5
+mauve C47FD5
+red E57474
+maroon E57474
+peach E59A84
+yellow E5C76B
+green 8CCFB0
+teal 6CBFBF
+sky 67B0E8
+sapphire 67B0E8
+blue 67B0E8
+lavender 67B0E8
+klink 67B0E8
+klinkSelection 67B0E8
+kvisited C47FD5
+kvisitedSelection C47FD5
+knegative E57474
+knegativeSelection E57474
+kneutral E5C76B
+kneutralSelection E5C76B
+kpositive 8CCFB0
+kpositiveSelection 8CCFB0
+text E8E8E8
+subtext1 B3B9BE
+subtext0 8A8F94
+overlay2 7A7F84
+overlay1 6A6F74
+overlay0 5A5F64
+surface2 2E3538
+surface1 232A2D
+surface0 1A2023
+base 141B1E
+mantle 0F1416
+crust 0A0E10
+success 8CCFB0
+onSuccess 141B1E
+successContainer 3A4145
+onSuccessContainer E8E8E8