feat(web): settings view for roots and policies

Own route beside library and queues. Roots edit kind, audience, path
and their policy; policies get a form over the real fields — size
bands as number inputs, score and source weights as numbers,
resolution preference and audio/HDR rules as validated lists. Delete
arms before firing; a 409 from a referenced policy or occupied root
surfaces its message.

web/src/style.css

@@ -1270,3 +1270,82 @@ body {
     width: 2.5rem;
   }
 }
+
+/* ---- settings (issue #116) -------------------------------------------- */
+
+/* rows follow the queues pattern: line, then an action pair */
+.settings-row-actions {
+  display: flex;
+  gap: var(--space-2);
+  margin: var(--space-1) 0 var(--space-2);
+}
+
+.form-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr));
+  gap: var(--space-3);
+  align-items: end;
+}
+
+.field {
+  display: grid;
+  gap: var(--space-1);
+}
+
+.field-label {
+  font-size: var(--text-2xs);
+  text-transform: uppercase;
+  letter-spacing: 0.12em;
+}
+
+.form-input {
+  min-height: 2.25rem;
+  width: 100%;
+  padding: 0 var(--space-2);
+  color: var(--ink);
+  font-family: var(--font-readout);
+  font-size: var(--text-xs);
+  background: var(--ground);
+  border: 1px solid var(--line);
+  border-radius: var(--radius);
+  box-shadow: inset 0 1px var(--lowlight);
+  caret-color: var(--accent);
+  transition: border-color 150ms var(--ease-out);
+}
+
+.form-input:hover {
+  border-color: var(--line-strong);
+}
+
+.form-input:focus {
+  border-color: var(--accent);
+  outline: none;
+}
+
+.form-input:disabled {
+  color: var(--ink-faint);
+  border-color: var(--line);
+}
+
+select.form-input {
+  appearance: none;
+}
+
+.form-input[data-invalid] {
+  border-color: var(--signal-fault);
+}
+
+/* one resolution's size band: label, floor, target, penalty on a line */
+.band-line {
+  display: flex;
+  align-items: center;
+  gap: var(--space-2);
+}
+
+.band-line .field-label {
+  width: 3.5rem;
+}
+
+.band-num {
+  width: 4.5rem;
+}