feat: extend module platform with UI slots, runtime components, CLI tooling and {{userId}} search support

Completes the generic module platform that enables modules to contribute
UI elements, runtime JS components, and search resources without any
core hardcoding.

New generic UI slot types:
- topbar.right_item: module-contributed topbar buttons
- layout.body_end_template: module-contributed dialog/overlay templates
- layout.head_style: module-contributed global CSS
- runtime.component: declarative JS component registration with phase ordering

New infrastructure:
- ModuleAutoloader: PSR-4 autoloading for module-local PHP classes
- ModuleRuntimePageBuilder: symlinks module pages into runtime directory
- ModuleRuntimeAssetPublisher: publishes module CSS/JS to web/modules/
- ModulePermissionSynchronizer: syncs module permissions to DB
- CLI scripts: module-runtime-sync, module-build, module-migrate,
  module-permissions-sync, module-assets-sync
- {{userId}} placeholder in SearchDataService for user-scoped search queries
- Component runtime with phased initialization (early/default/late)
- AppContainer.protectExistingBindings() to prevent module→core overwrites
- Architecture tests: ModuleStructureContractTest, CoreTemplateIsolationTest,
  FrontendComponentRuntimeContractTest, AppContainerIsolationContractTest

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/css/layout/app-shell.css

@@ -2769,10 +2769,6 @@
     overflow: auto;
   }
 
-  dialog > article > footer button {
-    margin-bottom: 0;
-  }
-
   .bi::before,
   [class^="bi-"]::before,
   [class*=" bi-"]::before {
@@ -2791,68 +2787,7 @@
     }
   }
 
-  dialog > article > header > * {
-    margin-bottom: 0;
-  }
-
-  dialog > article > header .close,
-  dialog > article > header :is(a, button)[rel="prev"] {
-    margin: 0;
-    margin-left: var(--app-spacing);
-    padding: 0;
-    float: right;
-  }
-
-  dialog > article > footer {
-    text-align: right;
-  }
-
-  dialog > article > footer [role="button"],
-  dialog > article > footer button {
-    margin-bottom: 0;
-  }
-
-  dialog > article > footer [role="button"]:not(:first-of-type),
-  dialog > article > footer button:not(:first-of-type) {
-    margin-left: calc(var(--app-spacing) * 0.5);
-  }
-
-  dialog > article .close,
-  dialog > article :is(a, button)[rel="prev"] {
-    display: block;
-    width: 1rem;
-    height: 1rem;
-    margin-top: calc(var(--app-spacing) * -1);
-    margin-bottom: var(--app-spacing);
-    margin-left: auto;
-    border: none;
-    background-image: var(--app-icon-close);
-    background-position: center;
-    background-size: auto 1rem;
-    background-repeat: no-repeat;
-    background-color: transparent;
-    opacity: 0.5;
-    transition: opacity var(--app-transition);
-  }
-
-  dialog
-    > article
-    .close:is(
-      [aria-current]:not([aria-current="false"]),
-      :hover,
-      :active,
-      :focus
-    ),
-  dialog
-    > article
-    :is(a, button)[rel="prev"]:is(
-      [aria-current]:not([aria-current="false"]),
-      :hover,
-      :active,
-      :focus
-    ) {
-    opacity: 1;
-  }
+  /* Dialog header/footer/close styles → web/css/components/app-dialog.css */
 
   dialog:not([open]),
   dialog[open="false"] {