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/slides/slide-form-template-lock.js

@@ -0,0 +1,86 @@
+export function createTemplateSelectorLockController(templateSelect) {
+  var locked = false;
+  var armed = false;
+  var lockInput = null;
+
+  function clearLockInput() {
+    if (lockInput && lockInput.parentNode) {
+      lockInput.parentNode.removeChild(lockInput);
+    }
+    lockInput = null;
+  }
+
+  function reset() {
+    locked = false;
+    armed = false;
+    clearLockInput();
+    if (!templateSelect) {
+      return;
+    }
+
+    templateSelect.disabled = false;
+    templateSelect.removeAttribute('aria-disabled');
+    templateSelect.removeAttribute('title');
+    templateSelect.classList.remove('is-locked');
+  }
+
+  function arm() {
+    armed = true;
+  }
+
+  function syncLockedValue() {
+    if (lockInput) {
+      lockInput.value = templateSelect.value;
+    }
+  }
+
+  function lock() {
+    if (!templateSelect || locked) {
+      return;
+    }
+
+    locked = true;
+    lockInput = lockInput || document.createElement('input');
+    lockInput.type = 'hidden';
+    lockInput.name = templateSelect.name;
+    lockInput.value = templateSelect.value;
+    templateSelect.insertAdjacentElement('afterend', lockInput);
+    templateSelect.disabled = true;
+    templateSelect.setAttribute('aria-disabled', 'true');
+    templateSelect.setAttribute('title', 'Template is locked after you edit its content.');
+    templateSelect.classList.add('is-locked');
+  }
+
+  function markEdited() {
+    if (!armed) {
+      return false;
+    }
+
+    lock();
+    syncLockedValue();
+    return locked;
+  }
+
+  function sync() {
+    if (!templateSelect) {
+      return false;
+    }
+
+    if (locked) {
+      syncLockedValue();
+      return true;
+    }
+
+    return false;
+  }
+
+  return {
+    reset: reset,
+    arm: arm,
+    markEdited: markEdited,
+    sync: sync,
+    isLocked: function () {
+      return locked;
+    }
+  };
+}