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/tokyonight/medium/dark.txt

@@ -0,0 +1,110 @@
+primary_paletteKeyColor 7AA2F7
+secondary_paletteKeyColor 9ECE6A
+tertiary_paletteKeyColor BB9AF7
+neutral_paletteKeyColor 1A1B26
+neutral_variant_paletteKeyColor 292E42
+background 1A1B26
+onBackground C0CAF5
+surface 24283B
+surfaceDim 16161E
+surfaceBright 3B4261
+surfaceContainerLowest 0F0F14
+surfaceContainerLow 2B3048
+surfaceContainer 2A2F41
+surfaceContainerHigh 3B4261
+surfaceContainerHighest 414868
+onSurface C0CAF5
+surfaceVariant 2A2F41
+onSurfaceVariant A9B1D6
+inverseSurface C0CAF5
+inverseOnSurface 1A1B26
+outline 565F89
+outlineVariant 3B4261
+shadow 000000
+scrim 000000
+surfaceTint 7AA2F7
+primary 7AA2F7
+onPrimary 1A1B26
+primaryContainer 3B4261
+onPrimaryContainer 7AA2F7
+inversePrimary 5A7FD7
+secondary 9ECE6A
+onSecondary 1A1B26
+secondaryContainer 3B4261
+onSecondaryContainer 9ECE6A
+tertiary BB9AF7
+onTertiary 1A1B26
+tertiaryContainer 3B4261
+onTertiaryContainer BB9AF7
+error F7768E
+onError 1A1B26
+errorContainer 4C3743
+onErrorContainer F7768E
+primaryFixed 7AA2F7
+primaryFixedDim 5A7FD7
+onPrimaryFixed 1A1B26
+onPrimaryFixedVariant 2A2F41
+secondaryFixed 9ECE6A
+secondaryFixedDim 7EAE4A
+onSecondaryFixed 1A1B26
+onSecondaryFixedVariant 2A2F41
+tertiaryFixed BB9AF7
+tertiaryFixedDim 9B7AD7
+onTertiaryFixed 1A1B26
+onTertiaryFixedVariant 2A2F41
+term0 1A1B26
+term1 F7768E
+term2 9ECE6A
+term3 E0AF68
+term4 7AA2F7
+term5 BB9AF7
+term6 7DCFFF
+term7 C0CAF5
+term8 565F89
+term9 F7768E
+term10 9ECE6A
+term11 E0AF68
+term12 7AA2F7
+term13 BB9AF7
+term14 7DCFFF
+term15 C0CAF5
+rosewater C0CAF5
+flamingo BB9AF7
+pink F7768E
+mauve BB9AF7
+red F7768E
+maroon E0AF68
+peach FF9E64
+yellow E0AF68
+green 9ECE6A
+teal 1ABC9C
+sky 7DCFFF
+sapphire 2AC3DE
+blue 7AA2F7
+lavender 7DCFFF
+klink 7AA2F7
+klinkSelection 7AA2F7
+kvisited BB9AF7
+kvisitedSelection BB9AF7
+knegative F7768E
+knegativeSelection F7768E
+kneutral E0AF68
+kneutralSelection E0AF68
+kpositive 9ECE6A
+kpositiveSelection 9ECE6A
+text C0CAF5
+subtext1 A9B1D6
+subtext0 9AA5CE
+overlay2 787C99
+overlay1 696D85
+overlay0 565F89
+surface2 2A2F41
+surface1 24283B
+surface0 1A1B26
+base 1A1B26
+mantle 16161E
+crust 0F0F14
+success 9ECE6A
+onSuccess 1A1B26
+successContainer 3B4261
+onSuccessContainer C0CAF5