feat: two-step staging upload + multi-page PDF person inheritance

- Add stage/process-staged/remove-staged endpoints for batch upload workflow
- Add staging gallery UI with thumbnail previews and per-image removal
- Inherit person info & doc fields from page 1 for multi-page PDFs
- Auto-link page 2+ to same person on confirmation
- Show info banner on review page for multi-page documents
- Exclude staged docs from stats counters

static/css/main.css

@@ -355,6 +355,20 @@ a.stat.active { border-color: rgba(15,118,110,.24); background: var(--primary-so
   margin-bottom: 1rem;
   color: var(--success);
 }
+.info-banner {
+  background: linear-gradient(135deg, rgba(239,246,255,.95), rgba(255,255,255,.82));
+  border: 1px solid #bfdbfe;
+  border-radius: calc(var(--radius) - 4px);
+  padding: .85rem 1rem;
+  margin-bottom: 1rem;
+  color: #1d4ed8;
+  display: flex;
+  align-items: center;
+  gap: .6rem;
+  font-size: .92rem;
+  line-height: 1.5;
+}
+.info-banner svg { flex-shrink: 0; stroke: #3b82f6; }
 
 /* ============================
    Upload Card
@@ -1450,3 +1464,107 @@ a.stat.active { border-color: rgba(15,118,110,.24); background: var(--primary-so
     font-size: .68rem;
   }
 }
+
+/* ============================
+   Staging Gallery (two-step upload)
+   ============================ */
+.stage-controls {
+  display: flex;
+  gap: .75rem;
+  flex-wrap: wrap;
+  margin-bottom: 1rem;
+}
+.stage-capture-btn svg { vertical-align: -.15em; margin-inline-end: .3rem; }
+
+.staging-gallery {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
+  gap: .75rem;
+  margin-bottom: 1rem;
+}
+.staging-thumb {
+  position: relative;
+  border-radius: var(--radius-sm);
+  overflow: hidden;
+  background: var(--surface-tint);
+  border: 2px solid var(--border);
+  aspect-ratio: 3/4;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  transition: var(--transition);
+}
+.staging-thumb.loading {
+  opacity: .6;
+}
+.staging-thumb.removing {
+  opacity: 0;
+  transform: scale(.9);
+}
+.staging-thumb img {
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+}
+.staging-thumb-name {
+  font-size: .72rem;
+  color: var(--text-muted);
+  padding: .25rem .4rem;
+  text-align: center;
+  position: absolute;
+  bottom: 0;
+  left: 0;
+  right: 0;
+  background: rgba(255,255,255,.85);
+  backdrop-filter: blur(4px);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.staging-remove {
+  position: absolute;
+  top: 4px;
+  left: 4px;
+  width: 26px;
+  height: 26px;
+  border-radius: 50%;
+  border: none;
+  background: rgba(220,38,38,.85);
+  color: #fff;
+  font-size: 1.1rem;
+  line-height: 1;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  opacity: 0;
+  transition: opacity .15s;
+}
+.staging-thumb:hover .staging-remove { opacity: 1; }
+@media (pointer: coarse) { .staging-remove { opacity: 1; } }
+
+.staging-thumb-spinner {
+  width: 28px;
+  height: 28px;
+  border: 3px solid var(--border);
+  border-top-color: var(--primary);
+  border-radius: 50%;
+  animation: spin .7s linear infinite;
+}
+@keyframes spin { to { transform: rotate(360deg); } }
+
+.staging-count {
+  text-align: center;
+  font-weight: 600;
+  color: var(--primary-dark);
+  margin-bottom: .75rem;
+  font-size: 1rem;
+}
+
+.stage-action-buttons {
+  display: flex;
+  gap: .5rem;
+  justify-content: center;
+  margin-top: .75rem;
+}