Server web UI: make photo-card dragging actually feel like dragging

The card being dragged never moved -- it just faded in place while a
static outline highlighted whatever was underneath the finger. Now the
card tracks the pointer 1:1 (translate + a slight scale-up "lift"),
gets a stronger shadow while airborne, and leaves its grid slot looking
like an empty gap until dropped (transform doesn't remove it from
layout flow, so the reserved space stays put -- no reflow needed until
drop). pointer-events:none while dragging so elementFromPoint's
drop-target hit-test sees through to the card underneath instead of
hitting the translated one.

Also: a short vibration tick when the touch hold-to-arm fires and
another on a successful drop (Chrome/Android only, iOS Safari has no
Vibration API -- harmless no-op there), and trimmed the arm delay from
350ms to 250ms now that there's actual feedback confirming the hold
registered.

server/app/templates/base.html

@@ -261,8 +261,20 @@
     }
     .photo-card:hover { box-shadow: var(--shadow-hover); transform: translateY(-1px); }
     .photo-card:active { cursor: grabbing; }
-    .photo-card.dragging { opacity: 0.35; }
-    .photo-card.drag-armed { box-shadow: 0 0 0 3px var(--focus-ring) inset; }
+    .photo-card.drag-armed {
+      box-shadow: 0 0 0 3px var(--focus-ring) inset;
+      transform: scale(0.97);
+    }
+    /* No transform transition here -- the JS drives transform on every
+       pointermove to track the finger 1:1, and the .15s base transition
+       would otherwise make it visibly lag behind a fast swipe. */
+    .photo-card.dragging {
+      z-index: 20;
+      box-shadow: 0 16px 32px rgba(0, 0, 0, 0.35);
+      transition: box-shadow .15s ease;
+      pointer-events: none; /* so elementFromPoint hits the card underneath, not this one */
+      cursor: grabbing;
+    }
     .photo-card.drag-over { outline: 3px solid var(--accent); outline-offset: -3px; }
     .photo-card img { width: 100%; height: 100%; object-fit: cover; display: block; pointer-events: none; }
     .photo-card .badge { position: absolute; top: 6px; left: 6px; background: var(--overlay); color: white; font-size: 10px; padding: 2px 6px; border-radius: 4px; }

server/app/templates/index.html

@@ -207,9 +207,16 @@
     // hold entirely (no scroll-vs-drag ambiguity with a mouse).
     let dragState = null; // { pointerId, fromIndex, toIndex, moved, armed, holdTimer }
     const DRAG_START_THRESHOLD_PX = 6; // ignore tiny jitter once armed, before committing to a drag
-    const DRAG_HOLD_MS = 350;
+    const DRAG_HOLD_MS = 250;
     const HOLD_CANCEL_THRESHOLD_PX = 10; // movement before the hold timer fires -> treat as a scroll, not a drag
 
+    function vibrate(ms) {
+      // Chrome/Android only -- iOS Safari has no Vibration API. Wrapped so
+      // it's a harmless no-op everywhere else rather than needing a
+      // feature check at every call site.
+      try { navigator.vibrate?.(ms); } catch (e) { /* ignore */ }
+    }
+
     function clearDragOverStyling() {
       document.querySelectorAll('.photo-card.drag-over').forEach((el) => el.classList.remove('drag-over'));
     }
@@ -219,9 +226,11 @@
         clearTimeout(dragState.holdTimer);
       }
       card.style.touchAction = '';
+      card.style.transform = '';
       card.classList.remove('dragging', 'drag-armed');
       clearDragOverStyling();
       if (dragState && dragState.moved && dragState.toIndex !== undefined && dragState.toIndex !== dragState.fromIndex) {
+        vibrate(15);
         moveItem(dragState.fromIndex, dragState.toIndex);
       }
       dragState = null;
@@ -287,6 +296,7 @@
                 dragState.armed = true;
                 card.classList.add('drag-armed');
                 card.style.touchAction = 'none';
+                vibrate(10);
                 try { card.setPointerCapture(e.pointerId); } catch (err) { /* pointer may have already left */ }
               }
             }, DRAG_HOLD_MS);
@@ -313,9 +323,10 @@
             return;
           }
 
+          const dx = e.clientX - dragState.startX;
+          const dy = e.clientY - dragState.startY;
+
           if (!dragState.moved) {
-            const dx = e.clientX - dragState.startX;
-            const dy = e.clientY - dragState.startY;
             if (Math.hypot(dx, dy) < DRAG_START_THRESHOLD_PX) {
               return;
             }
@@ -323,6 +334,12 @@
             card.classList.remove('drag-armed');
             card.classList.add('dragging');
           }
+
+          // Follows the finger 1:1 -- the actual "pick it up and carry it"
+          // feedback that was missing before (the card used to just fade
+          // in place while a static outline highlighted the drop target).
+          card.style.transform = `translate(${dx}px, ${dy}px) scale(1.06)`;
+
           const overCard = document.elementFromPoint(e.clientX, e.clientY)?.closest('.photo-card');
           clearDragOverStyling();
           if (overCard && overCard !== card) {