Rebuild DEEG as a fifth installation, add stepped forms and a plugin system, and clear the review backlog

Forms gained steps, conditions, image choices, number fields with units and a
summary step; the DEEG price finder uses all of it. Plugins are manifest plus
Twig: blocks, settings, containers, routes, presets and theme packs, switched
per installation. The review backlog is done: archive pages render through the
normal page pipeline, forms and post lists work inside areas and sections,
repeated sections get their own ids, breakpoints and colours come from the
palette, backup and update work on MySQL and lock each other out.

The task worker no longer shortens a process that has no time limit:
set_time_limit() sets the limit instead of extending it, which turned an
unlimited CLI run into eighty seconds and killed the full test suite far away
from the scheduler.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Content/Theme.php

@@ -311,6 +311,21 @@ final class Theme
         return null;
     }
 
+    /** Die relative Leuchtdichte einer Hexfarbe nach WCAG; 0 fuer Schwarz, 1 fuer Weiss, 0.5 wenn unlesbar. */
+    public static function luminance(string $hex): float
+    {
+        if (1 !== preg_match('/^#([0-9a-f]{6})/i', $hex, $m)) {
+            return 0.5;
+        }
+        $kanal = static function (int $wert): float {
+            $c = $wert / 255;
+
+            return $c <= 0.03928 ? $c / 12.92 : (($c + 0.055) / 1.055) ** 2.4;
+        };
+
+        return 0.2126 * $kanal(hexdec(substr($m[1], 0, 2))) + 0.7152 * $kanal(hexdec(substr($m[1], 2, 2))) + 0.0722 * $kanal(hexdec(substr($m[1], 4, 2)));
+    }
+
     public function css(array $theme): string
     {
         $variables = [];
@@ -344,6 +359,17 @@ final class Theme
         $variables[] = sprintf('--muted:var(--k-muted,color-mix(in srgb,%s 80%%,%s))', $ink, $paper);
         $variables[] = sprintf('--line:var(--k-line,color-mix(in srgb,%s 20%%,%s))', $ink, $paper);
         $variables[] = sprintf('--mint:var(--k-mint,color-mix(in srgb,%s 14%%,%s))', $colour($base['linkColor']), $paper);
+        // Dunkle Palette: Formularfelder, Rollbalken und Fehlermeldungen folgen ihr. Das Rot fuer
+        // Fehler war fest auf Weiss gedacht; auf dunklem Grund ist es unlesbar. Also je nach
+        // Helligkeit des Papiers ein Rot, das dort steht - und der Hintergrund der Meldung aus
+        // Rot und Papier gemischt statt aus einem festen Hellrosa.
+        // Fuer die Leuchtdichte braucht es den Hexwert, nicht den Verweis var(--k-...).
+        $hexwert = static fn (string $wert): string => str_starts_with($wert, '@') ? (string) (array_column($theme['colors'], 'value', 'key')[substr($wert, 1)] ?? '#ffffff') : $wert;
+        $dunkel = self::luminance($hexwert($base['backgroundColor'])) < 0.4;
+        $variables[] = '--k-scheme:'.($dunkel ? 'dark' : 'light');
+        $variables[] = '--k-error:'.($dunkel ? '#ff9b8a' : '#8b2f22');
+        $variables[] = sprintf('--k-error-bg:color-mix(in srgb,%s 12%%,%s)', $dunkel ? '#ff9b8a' : '#8b2f22', $hexwert($base['backgroundColor']));
+        $variables[] = sprintf('--k-error-line:color-mix(in srgb,%s 45%%,%s)', $dunkel ? '#ff9b8a' : '#8b2f22', $hexwert($base['backgroundColor']));
 
         $scale = (float) $base['headingScale'];
         $headings = '';