feat: add file upload for materials (PDF/DOCX) with ingestion pipeline

internal/webapp/static/styles.css

@@ -362,6 +362,88 @@ button.is-loading .btn-spinner { display:inline-block; }
   margin:0; padding:12px; white-space:pre-wrap; font-size:12px; line-height:1.5; color:var(--text);
 }
 
+/* ===== FILE UPLOAD ===== */
+.file-upload-row {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  grid-column: 1 / -1;
+}
+
+.file-label {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  font-size: 13px;
+  font-weight: 650;
+  color: var(--muted);
+}
+
+.file-label input[type="file"] {
+  padding: 8px;
+  font-size: 12px;
+  border: 1px solid var(--line);
+  border-radius: 6px;
+  background: #fbfcfa;
+  color: var(--text);
+  cursor: pointer;
+  min-width: 200px;
+}
+
+.file-label input[type="file"]::file-selector-button {
+  border: 1px solid var(--line);
+  border-radius: 4px;
+  padding: 6px 10px;
+  background: var(--surface);
+  color: var(--text);
+  cursor: pointer;
+  font-size: 12px;
+  font-weight: 650;
+  margin-right: 10px;
+}
+
+.file-label input[type="file"]::file-selector-button:hover {
+  background: var(--surface-muted);
+}
+
+.file-name {
+  font-size: 12px;
+  color: var(--muted);
+  flex: 1;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.paste-toggle {
+  grid-column: 1 / -1;
+  border: 1px solid var(--line);
+  border-radius: 6px;
+  padding: 10px 14px;
+  background: #fbfcfa;
+}
+
+.paste-toggle summary {
+  cursor: pointer;
+  color: var(--muted);
+  font-size: 12px;
+  font-weight: 650;
+}
+
+.paste-toggle[open] summary {
+  margin-bottom: 12px;
+}
+
+.paste-toggle .wide-field {
+  grid-column: 1 / -1;
+}
+
+.small-button {
+  min-height: 32px;
+  padding: 0 14px;
+  font-size: 12px;
+}
+
 /* ===== RESPONSIVE ===== */
 @media (max-width:900px) {
   .main-grid { grid-template-columns:1fr; }