feat(library): exclude configured folders from scanning and analysis

apps/web/src/pages/admin/library.module.css

@@ -238,6 +238,20 @@
   gap: 6px;
 }
 
+.excludedDirs {
+  width: 100%;
+  box-sizing: border-box;
+  resize: vertical;
+  border: 1px solid var(--line2);
+  border-radius: var(--radius-md);
+  padding: 10px 12px;
+  background: var(--surface2);
+  color: var(--text);
+  font: 13px var(--font-mono);
+}
+.excludedDirs:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
+.excludedDirs:disabled { opacity: 0.6; }
+
 .tiles {
   display: grid;
   grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));