refactor(theme): drop dark-green and collapse theme registry to light/dark

Remove the extensible theme catalog (config/themes.php + ThemeConfigGateway)
in favor of a two-entry const on SettingsAppGateway. appThemes() now returns
the list directly — no container lookup, no file include. Drop the
dark-green theme assets, narrow [data-theme^="dark"] selectors to
[data-theme="dark"], and tighten isDarkTheme() to an exact match. Ship an
idempotent migration that corrects any leftover 'dark-green' rows on users
and tenants to safe defaults (light / NULL).

Tenant scoping (default_theme, allow_user_theme) and per-user override stay
intact; only the catalog extensibility and the third theme are removed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/css/base/variables.base.css

@@ -602,7 +602,7 @@
   }
 }
 
-[data-theme^="dark"] {
+[data-theme="dark"] {
   color-scheme: dark;
   --app-background-color: rgb(19, 22.5, 30.5);
   --app-sidebar-background-color: var(--app-background-color);
@@ -830,7 +830,7 @@
   --app-icon-invalid: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='rgb(149.5, 74, 80)' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='12' r='10'%3E%3C/circle%3E%3Cline x1='12' y1='8' x2='12' y2='12'%3E%3C/line%3E%3Cline x1='12' y1='16' x2='12.01' y2='16'%3E%3C/line%3E%3C/svg%3E");
 }
 
-[data-theme^="dark"]
+[data-theme="dark"]
   input:is(
     [type="submit"],
     [type="button"],

web/css/base/variables.contrast.css

@@ -37,8 +37,8 @@ html[data-contrast="high"][data-theme="light"],
   --app-action-danger-outline-background: rgba(143, 0, 0, 0.2);
 }
 
-html[data-contrast="high"][data-theme^="dark"],
-[data-contrast="high"][data-theme^="dark"] {
+html[data-contrast="high"][data-theme="dark"],
+[data-contrast="high"][data-theme="dark"] {
   --app-background-color: #000;
   --app-sidebar-background-color: var(--app-background-color);
   --app-color: #f8fafc;

web/css/base/variables.theme-dark-green.css

@@ -1,45 +0,0 @@
-@charset "UTF-8";
-
-@layer tokens {
-[data-theme="dark-green"] {
-  --app-background-color: #0f1713;
-  --app-sidebar-background-color: var(--app-background-color);
-  --app-color: #cfe0d6;
-  --app-text-selection-color: rgba(64, 170, 118, 0.25);
-  --app-muted-color: #8a9b91;
-  --app-muted-border-color: #223028;
-  --app-form-element-background-color: #141f19;
-  --app-form-element-border-color: #26362d;
-  --app-form-element-color: #d5e6dc;
-  --app-form-element-placeholder-color: #7f9187;
-  --app-card-background-color: #141f19;
-  --app-card-border-color: #223028;
-  --app-card-sectioning-background-color: #1a261f;
-  --app-details-card-open-summary-bg: #203026;
-  --app-dropdown-background-color: #141f19;
-  --app-dropdown-border-color: #223028;
-  --app-dropdown-hover-background-color: #1f2a24;
-  --app-modal-overlay-background-color: rgba(7, 10, 8, 0.75);
-  --app-progress-background-color: #223028;
-  --app-primary-h-base: 145;
-  --app-primary-s-base: 38%;
-  --app-primary-l-base: 38%;
-  --badge-success-bg: #123225;
-  --badge-success-color: #8de2b4;
-  --badge-success-border: #1f4a36;
-  --badge-danger-bg: #361a1d;
-  --badge-danger-color: #f4a3ad;
-  --badge-danger-border: #5a2b32;
-  --badge-info-bg: #142735;
-  --badge-info-color: #9ad2e0;
-  --badge-info-border: #214156;
-  --badge-warn-bg: #3a2a12;
-  --badge-warn-color: #ffdf9e;
-  --badge-warn-border: #5a401b;
-  --badge-neutral-bg: #1b2620;
-  --badge-neutral-color: #cfe0d6;
-  --badge-neutral-border: #2a3a31;
-  --app-tile-bg: rgb(20 28 24);
-  --app-blockquote-background-color: rgb(20 28 24);
-}
-}

web/css/vendor-overrides/gridjs.css

@@ -691,11 +691,6 @@
     filter: invert(1);
   }
 
-  html[data-theme="dark-green"] button.gridjs-sort,
-  html[data-theme="dark-green"] button.gridjs-sort-neutral {
-    filter: invert(1);
-  }
-
   button.gridjs-sort {
     background-color: transparent;
     background-position-x: center;