Search filters for size (MB) and file extensions

- API: min_size and max_size in MB, ext as a comma-separated list. An
  extension matches as a whole word in search_text (file and entry names,
  dots as spaces), so "iso" finds .iso files but not "ISOLATION", which a
  plain search word matched as a substring. The trigram index serves it.
- Web UI: a size range and an extension field in the filter row, kept in
  the URL like the other filters.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/app.css

@@ -238,6 +238,43 @@ kbd {
   cursor: pointer;
 }
 
+/* A chip holding inputs: size bounds and file extensions. */
+.field-chip {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  height: 32px;
+  padding: 0 6px 0 13px;
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  background: var(--surface);
+  font-size: 13px;
+  color: var(--muted);
+}
+
+.field-chip:focus-within {
+  border-color: var(--accent);
+}
+
+.field-chip input {
+  width: 64px;
+  height: 24px;
+  padding: 0 6px;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  background: var(--surface-2);
+  color: var(--text);
+  font: inherit;
+}
+
+.field-chip input.ext {
+  width: 96px;
+}
+
+.field-chip .unit {
+  padding-right: 7px;
+}
+
 .chip[aria-pressed='true'],
 .chip-active {
   border-color: var(--accent);