Theme btop and Homepage via matugen on the mediaserver

Share the wallpaper symlink across all hosts by moving it from gnome.nix
into home-manager/fred.nix, and add matugen templates for btop and the
Homepage dashboard.

The Homepage NixOS module writes custom.css into /etc (read-only), so
bind-mount /var/lib/homepage-custom-css/custom.css over it. A systemd
path unit restarts homepage-dashboard whenever matugen rewrites the
file, so regeneration works without sudo.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/btop.theme

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+# Matugen-generated btop theme based on wallpaper
+
+theme[main_bg]="{{colors.surface.default.hex}}"
+theme[main_fg]="{{colors.on_surface.default.hex}}"
+theme[title]="{{colors.on_surface.default.hex}}"
+theme[hi_fg]="{{colors.primary.default.hex}}"
+theme[selected_bg]="{{colors.surface_container_high.default.hex}}"
+theme[selected_fg]="{{colors.primary.default.hex}}"
+theme[inactive_fg]="{{colors.on_surface_variant.default.hex}}"
+theme[graph_text]="{{colors.on_surface.default.hex}}"
+theme[meter_bg]="{{colors.surface_container.default.hex}}"
+theme[proc_misc]="{{colors.tertiary.default.hex}}"
+
+theme[cpu_box]="{{colors.outline.default.hex}}"
+theme[mem_box]="{{colors.outline.default.hex}}"
+theme[net_box]="{{colors.outline.default.hex}}"
+theme[proc_box]="{{colors.outline.default.hex}}"
+theme[div_line]="{{colors.outline_variant.default.hex}}"
+
+theme[temp_start]="{{colors.tertiary.default.hex}}"
+theme[temp_mid]="{{colors.secondary.default.hex}}"
+theme[temp_end]="{{colors.error.default.hex}}"
+
+theme[cpu_start]="{{colors.primary.default.hex}}"
+theme[cpu_mid]="{{colors.secondary.default.hex}}"
+theme[cpu_end]="{{colors.tertiary.default.hex}}"
+
+theme[free_start]="{{colors.primary.default.hex}}"
+theme[free_mid]="{{colors.secondary.default.hex}}"
+theme[free_end]="{{colors.tertiary.default.hex}}"
+
+theme[cached_start]="{{colors.primary.default.hex}}"
+theme[cached_mid]="{{colors.secondary.default.hex}}"
+theme[cached_end]="{{colors.tertiary.default.hex}}"
+
+theme[available_start]="{{colors.primary.default.hex}}"
+theme[available_mid]="{{colors.secondary.default.hex}}"
+theme[available_end]="{{colors.tertiary.default.hex}}"
+
+theme[used_start]="{{colors.primary.default.hex}}"
+theme[used_mid]="{{colors.secondary.default.hex}}"
+theme[used_end]="{{colors.tertiary.default.hex}}"
+
+theme[download_start]="{{colors.primary.default.hex}}"
+theme[download_mid]="{{colors.secondary.default.hex}}"
+theme[download_end]="{{colors.tertiary.default.hex}}"
+
+theme[upload_start]="{{colors.primary.default.hex}}"
+theme[upload_mid]="{{colors.secondary.default.hex}}"
+theme[upload_end]="{{colors.tertiary.default.hex}}"
+
+theme[process_start]="{{colors.primary.default.hex}}"
+theme[process_mid]="{{colors.secondary.default.hex}}"
+theme[process_end]="{{colors.tertiary.default.hex}}"

templates/homepage.css

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+/* Matugen-generated Homepage theme based on wallpaper */
+
+/* Background + text for the whole dashboard */
+html, body, main, .information-widget {
+  background-color: {{colors.surface.default.hex}} !important;
+  color: {{colors.on_surface.default.hex}} !important;
+}
+
+/* Service and widget cards */
+#information-widgets > *,
+.services-group .service,
+.bookmark-group .bookmark,
+.information-widget-datetime,
+.information-widget-resources,
+.information-widget-search {
+  background-color: {{colors.surface_container.default.hex}} !important;
+  color: {{colors.on_surface.default.hex}} !important;
+  border-color: {{colors.outline_variant.default.hex}} !important;
+}
+
+/* Group headings */
+h1, h2, h3, .services-group h2, .bookmark-group h2 {
+  color: {{colors.on_surface.default.hex}} !important;
+}
+
+/* Muted / secondary text */
+.service-description, .bookmark-description,
+.service .service-sub, .information-widget .label {
+  color: {{colors.on_surface_variant.default.hex}} !important;
+}
+
+/* Search input */
+input, .search input[type="text"] {
+  background-color: {{colors.surface_container_high.default.hex}} !important;
+  color: {{colors.on_surface.default.hex}} !important;
+  border-color: {{colors.outline.default.hex}} !important;
+}
+
+/* Accent — used on highlights, progress bars, links */
+a, .service a:hover, .bookmark a:hover,
+.resources .resource .progress .progress-bar,
+button:hover, .service-container:hover {
+  color: {{colors.primary.default.hex}} !important;
+}
+
+.resources .resource .progress .progress-bar,
+.resources .resource .usage-bar-fill {
+  background-color: {{colors.primary.default.hex}} !important;
+}
+
+/* Dividers */
+hr, .service-container, .bookmark-container {
+  border-color: {{colors.outline_variant.default.hex}} !important;
+}
+
+/* Override Tailwind's slate palette so built-in theme uses wallpaper colors */
+:root {
+  --color-slate-50: {{colors.on_surface.default.hex}};
+  --color-slate-100: {{colors.on_surface.default.hex}};
+  --color-slate-200: {{colors.on_surface.default.hex}};
+  --color-slate-300: {{colors.on_surface_variant.default.hex}};
+  --color-slate-400: {{colors.on_surface_variant.default.hex}};
+  --color-slate-500: {{colors.outline.default.hex}};
+  --color-slate-600: {{colors.outline_variant.default.hex}};
+  --color-slate-700: {{colors.surface_container_high.default.hex}};
+  --color-slate-800: {{colors.surface_container.default.hex}};
+  --color-slate-900: {{colors.surface.default.hex}};
+  --color-slate-950: {{colors.surface.default.hex}};
+}