Add in-app confirmation dialog replacing window.confirm

src/app/components/ConfirmDialog.module.css

@@ -0,0 +1,92 @@
+.backdrop {
+  position: fixed;
+  inset: 0;
+  z-index: 1000; /* above the future feature-modal layer (discard-over-modal) */
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: var(--space-5);
+  background: rgb(0 0 0 / 0.5);
+}
+
+.dialog {
+  width: 100%;
+  max-width: 28rem;
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-4);
+  padding: var(--space-6);
+  background: var(--layer-01);
+  border: var(--border-width) solid var(--border);
+  border-radius: var(--radius);
+  /* Minimal shadow, reserved for true overlays (doc §09). */
+  box-shadow: 0 2px 12px rgb(0 0 0 / 0.3);
+}
+
+.title {
+  margin: 0;
+  font-size: 16px;
+  font-weight: 600;
+  color: var(--text);
+}
+
+.message {
+  margin: 0;
+  font-size: 14px;
+  line-height: 1.4;
+  color: var(--text-secondary);
+}
+
+.actions {
+  display: flex;
+  justify-content: flex-end;
+  gap: var(--space-3);
+  margin-top: var(--space-2);
+}
+
+.cancel,
+.confirm {
+  height: 40px;
+  padding: 0 var(--space-5);
+  border: var(--border-width) solid transparent;
+  border-radius: var(--radius);
+  font: inherit;
+  font-weight: 600;
+  cursor: pointer;
+  transition: background var(--dur-fast) var(--ease);
+}
+
+.cancel {
+  background: transparent;
+  border-color: var(--border-strong);
+  color: var(--text);
+}
+
+.cancel:hover {
+  background: var(--layer-02);
+}
+
+.confirm {
+  background: var(--accent);
+  color: var(--accent-contrast);
+}
+
+.confirm:hover {
+  background: var(--accent-hover);
+}
+
+.danger {
+  background: var(--support-error);
+  color: var(--on-status);
+}
+
+.danger:hover {
+  /* Slightly darken; the error token already carries the meaning. */
+  filter: brightness(0.92);
+}
+
+.cancel:focus-visible,
+.confirm:focus-visible {
+  outline: 2px solid var(--focus);
+  outline-offset: 2px;
+}