Log an event that happened "now" in one tap

Logging a quick pee/poo/meal/sleep boundary took two taps: open the note
dialog, then Save. Make a single tap on a quick-action log the event
immediately at the current time.

Non-weight quick actions now call addEvent(type, "", Date.now()) directly
and show a brief snackbar with Undo (deletes the just-added event) and Add
note (opens the edit dialog for it), so notes, photos and custom times are
never lost. Weigh-ins still open the dialog since they need a value.
addEvent now returns the created event so the snackbar can reference it.

src/style.css

@@ -696,3 +696,46 @@ input.switch:checked::after { transform: translateX(18px); }
   border: 1px solid rgba(255, 255, 255, 0.6);
 }
 .update-banner-btn:hover { filter: brightness(0.97); }
+
+/* ---------- quick-log snackbar ---------- */
+.snackbar {
+  position: fixed;
+  left: 50%;
+  bottom: calc(16px + env(safe-area-inset-bottom, 0));
+  transform: translate(-50%, 12px);
+  z-index: 60;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  max-width: calc(100% - 32px);
+  padding: 8px 8px 8px 16px;
+  background: var(--surface);
+  color: var(--text);
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  box-shadow: var(--shadow);
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 0.18s ease, transform 0.18s ease;
+}
+.snackbar[hidden] { display: none; }
+.snackbar.show {
+  opacity: 1;
+  transform: translate(-50%, 0);
+  pointer-events: auto;
+}
+.snackbar-msg {
+  font-size: 0.9rem;
+  font-weight: 500;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+.snackbar-action {
+  background: transparent;
+  color: var(--accent);
+  font-weight: 700;
+  padding: 6px 10px;
+  flex-shrink: 0;
+}
+.snackbar-action:hover { filter: none; background: var(--accent-soft); }