feat(client): add UI kit, data layer, app shell, and Table component

- design token system (Atlantis, Kimberly, Powder Ash palette)
- Button, Badge, Input, Select, Card, SidePanel, Breadcrumbs components
- generic typed Table<T> component with loading/empty states
- API data layer: typed fetch client for environments, keys, sessions, scenarios
- Vite dev proxy targeting server on port 13000
- App shell with SidePanel nav and four entity pages (Environments, Keys, Sessions, Scenarios)
- Storybook config with dark/light theme toggle and a11y addon

client/src/ui/Input/Input.module.css

@@ -0,0 +1,60 @@
+.wrapper {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-1);
+  font-family: var(--font-family);
+  width: 100%;
+}
+
+.label {
+  font-size: var(--font-size-sm);
+  font-weight: 500;
+  color: var(--color-text);
+}
+
+.input {
+  font-family: var(--font-family);
+  font-size: var(--font-size-md);
+  color: var(--color-text);
+  background: var(--color-bg);
+  border: var(--border-width) solid var(--color-border);
+  border-radius: var(--radius-md);
+  padding: var(--space-2) var(--space-3);
+  height: 36px;
+  width: 100%;
+  outline: none;
+  transition: border-color var(--transition), box-shadow var(--transition);
+}
+
+.input::placeholder {
+  color: var(--color-text-muted);
+}
+
+.input:focus {
+  border-color: var(--color-primary);
+  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
+}
+
+.input:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+  background: var(--color-bg-subtle);
+}
+
+.hasError {
+  border-color: var(--color-error-fg);
+}
+.hasError:focus {
+  border-color: var(--color-error-fg);
+  box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.2);
+}
+
+.hint {
+  font-size: var(--font-size-xs);
+  color: var(--color-text-muted);
+}
+
+.error {
+  font-size: var(--font-size-xs);
+  color: var(--color-error-fg);
+}