feat: add form and page platform

src/presentation/styles/theme.css

@@ -590,6 +590,141 @@
     line-height: 1.7;
   }
 
+  .page-template {
+    display: grid;
+    gap: 1.25rem;
+    min-width: 0;
+  }
+
+  .page-template__breadcrumb {
+    padding-block-start: 1rem;
+    color: var(--color-content-muted);
+    font-size: 0.9rem;
+  }
+
+  .page-template__heading {
+    display: grid;
+    min-width: 0;
+    grid-template-columns: minmax(0, 1fr) auto;
+    align-items: end;
+    gap: 1rem;
+  }
+
+  .page-template__heading .page-header {
+    grid-row: span 2;
+    min-width: 0;
+  }
+
+  .page-template__status,
+  .page-template__actions,
+  .status-page__actions,
+  .form-actions {
+    display: flex;
+    flex-wrap: wrap;
+    align-items: center;
+    justify-content: flex-end;
+    gap: 0.75rem;
+  }
+
+  .page-template__layout {
+    display: grid;
+    min-width: 0;
+    gap: 1.5rem;
+  }
+
+  .page-template__layout[data-has-aside="true"] {
+    grid-template-columns: minmax(0, 1fr) minmax(14rem, 20rem);
+  }
+
+  .page-template__content,
+  .page-template__aside,
+  .collection-page__results,
+  .detail-page__sections,
+  .form-page__fields {
+    min-width: 0;
+  }
+
+  .page-template__aside,
+  .detail-page__metadata,
+  .collection-page__toolbar,
+  .form-error-summary {
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius-surface);
+    padding: 1rem;
+    background: var(--color-panel);
+  }
+
+  .collection-page__toolbar,
+  .collection-page__active-filters,
+  .collection-page__bulk-actions {
+    display: flex;
+    flex-wrap: wrap;
+    align-items: end;
+    gap: 0.75rem;
+  }
+
+  .collection-page__result-count {
+    color: var(--color-content-muted);
+  }
+
+  .collection-page__results,
+  .detail-page__sections,
+  .form-page__fields,
+  .form-page__error-summary {
+    display: grid;
+    gap: 1rem;
+  }
+
+  .collection-page__pagination {
+    margin-block-start: 1.25rem;
+  }
+
+  .detail-page__danger {
+    margin-block-start: 2rem;
+    border-top: 1px solid var(--color-danger-border);
+    padding-block-start: 1rem;
+  }
+
+  .form-error-summary {
+    border-color: var(--color-danger-border);
+    background: var(--color-danger-surface);
+  }
+
+  .form-error-summary h2 {
+    font-size: 1.1rem;
+  }
+
+  .form-error-summary p,
+  .form-error-summary ul {
+    margin-block-end: 0;
+  }
+
+  .form-actions {
+    padding-block-start: 1rem;
+    border-top: 1px solid var(--color-border);
+  }
+
+  .form-actions--sticky {
+    position: sticky;
+    z-index: 10;
+    bottom: 0;
+    padding: 0.75rem;
+    background: color-mix(in oklch, var(--color-panel) 94%, transparent);
+  }
+
+  .status-page {
+    max-width: 48rem;
+    padding-block: 2rem;
+  }
+
+  .status-page__actions {
+    justify-content: flex-start;
+  }
+
+  .status-page__support {
+    color: var(--color-content-muted);
+  }
+
   .readiness-grid {
     display: grid;
     grid-template-columns: repeat(3, minmax(0, 1fr));
@@ -832,6 +967,24 @@
   .component-grid--three {
     grid-template-columns: minmax(0, 1fr);
   }
+
+  .page-template__heading,
+  .page-template__layout[data-has-aside="true"] {
+    grid-template-columns: minmax(0, 1fr);
+  }
+
+  .page-template__heading .page-header {
+    grid-row: auto;
+  }
+
+  .page-template__actions,
+  .page-template__status {
+    justify-content: flex-start;
+  }
+
+  .form-actions--sticky {
+    margin-inline: calc(var(--spacing-page) * -1);
+  }
 }
 
 @media (prefers-reduced-motion: reduce) {