feat: add scoped theme builder system with per-route, per-module, and multi-site support

- Add theme_scopes and theme_scope_values database tables for scoped themes
- Implement theme resolver engine with inheritance: global > site > module > route
- Add module detection for 20+ routes (shop, guilds, radio, news, etc.)
- Create admin UI at /admin/theme-builder with scope tree and color editor
- Add ScopedThemeVars component for injecting scoped CSS via data-attributes
- Add ThemeScopeDetector client component for runtime module/route detection
- Add site-resolver for multi-site domain detection
- Add /api/themes/export endpoint (JSON, CSS, variables formats)
- Add /api/themes/export/embed.js for external integration widget
- Add server actions for full CRUD on scopes and theme values
- Add admin nav link and EN/NL translations

drizzle/migrations/0023_theme_builder_scopes.sql

@@ -0,0 +1,37 @@
+-- Theme Builder: scoped theme system for per-route, per-module, and multi-site theming.
+-- Idempotent: safe to re-run.
+
+CREATE TABLE IF NOT EXISTS theme_scopes (
+  id          BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+  name        VARCHAR(100) NOT NULL,
+  type        ENUM('global','site','module','route') NOT NULL,
+  parent_id   BIGINT UNSIGNED NULL,
+  site_domain VARCHAR(255) NULL,
+  route_path  VARCHAR(255) NULL,
+  module_id   VARCHAR(100) NULL,
+  is_active   TINYINT(1) NOT NULL DEFAULT 1,
+  sort_order  INT NOT NULL DEFAULT 0,
+  created_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  PRIMARY KEY (id),
+  KEY theme_scopes_parent_idx (parent_id),
+  KEY theme_scopes_type_idx (type),
+  UNIQUE KEY theme_scopes_unique_lookup (type, site_domain, route_path, module_id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS theme_scope_values (
+  id           BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
+  scope_id     BIGINT UNSIGNED NOT NULL,
+  setting_key  VARCHAR(100) NOT NULL,
+  setting_val  VARCHAR(255) NOT NULL,
+  mode         ENUM('light','dark') NOT NULL DEFAULT 'light',
+  created_at   DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at   DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  PRIMARY KEY (id),
+  UNIQUE KEY theme_scope_values_unique (scope_id, setting_key, mode),
+  KEY theme_scope_values_scope_idx (scope_id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+-- Seed: create the global scope from existing website_settings theme data.
+INSERT IGNORE INTO theme_scopes (id, name, type, parent_id, is_active, sort_order)
+VALUES (1, 'Global', 'global', NULL, 1, 0);