This PR breaks the large web and player bootstrap files into smaller modules with clearer ownership.

Web changes:

Split shared helpers, bootstrap logic, route groups, and upload-sync behavior out of web.js.
Kept web.js focused on wiring and server startup.
Fixed screen playlist reassignment so changing a screen’s playlist now triggers a refresh.
Fixed single-slide playlist refresh behavior so updates do not get stuck behind the current slide.
Player changes:

Split websocket/runtime handling into runtime.js.
Split playlist assembly and revision hashing into playlist.js.
Split onboarding and player HTTP routes into dedicated modules.
Split render utilities and template loading into render-helpers.js.
Kept player.js mostly as startup/orchestration.
Validation:

Rebuilt both services with Docker Compose.
Smoke-checked web and player routes after the refactor.
Verified get_errors was clean on the touched modules.

src/web/public/js/theme-sidebar.js

@@ -33,7 +33,7 @@
     var nextTheme = normalizedTheme === 'dark' ? 'light' : 'dark';
     var nextThemeLabel = nextTheme === 'dark' ? 'Dark mode' : 'Light mode';
 
-    document.documentElement.dataset.theme = normalizedTheme;
+    document.documentElement.dataset.bsTheme = normalizedTheme;
     document.documentElement.style.colorScheme = normalizedTheme;
 
     Array.prototype.forEach.call(document.querySelectorAll('[data-theme-toggle]'), function (toggleButton) {
@@ -62,7 +62,7 @@
 
     Array.prototype.forEach.call(toggleButtons, function (toggleButton) {
       toggleButton.addEventListener('click', function () {
-        var nextTheme = document.documentElement.dataset.theme === 'dark' ? 'light' : 'dark';
+        var nextTheme = document.documentElement.dataset.bsTheme === 'dark' ? 'light' : 'dark';
         setStoredTheme(nextTheme);
         applyTheme(nextTheme);
       });