feat(policies): backend-driven policy enforcement (frontend) (#6598)

## Summary
Adds the **Policies** feature (proprietary, behind the
`POLICIES_ENABLED` flag): backend-driven enforcement that runs a fixed
tool pipeline on documents, docked in the right tool sidebar alongside
Tools.

## Highlights
- **Policy catalog** — 5 categories; **Security** is wired (redact PII +
sanitize), the others are marked "Coming soon".
- **Backend as source of truth** — policies persist via the Policies
engine (`/api/v1/policies`), one policy per category, with a local cache
+ offline fallback.
- **Auto-run** — enabled policies run on every uploaded file: dispatch →
poll → import outputs into the workspace.
- **Security redact config** — PII preset dropdown + custom word/regex
entry + advanced options; tool params map to the backend endpoint
fields.
- **Activity feed** with retry on failures; **file badges** showing
which policies ran on a file (sidebar + files page), tinted to the
policy colour.
- Reuses the **Watched Folders** engine for each policy's backing
folder; policy-owned folders are filtered out of the Watched Folders UI.

## Notes
- Gated by `POLICIES_ENABLED` (true in proprietary, false in core) —
unreachable in the open-source build.
- Frontend-only diff; depends on the backend Policies engine and the
merged Watched Folders feature.

frontend/shared/components/SettingsRow.tsx

@@ -0,0 +1,39 @@
+import type { ReactNode } from "react";
+import "@shared/components/SettingsRow.css";
+
+export interface SettingsRowProps {
+  /** Left-aligned setting name. */
+  label: ReactNode;
+  /** Optional secondary line under the label. */
+  description?: ReactNode;
+  /** Right-aligned control (toggle / select / input / button). */
+  control: ReactNode;
+  className?: string;
+}
+
+/**
+ * Horizontal settings row: label (+ optional description) on the left, control
+ * right-aligned. The companion to vertical {@link FormField} — use this for the
+ * label-left/control-right settings pattern (the layout ToggleSwitch's docs
+ * point at). Stack rows inside a {@code Card padding="none"} for a settings list.
+ */
+export function SettingsRow({
+  label,
+  description,
+  control,
+  className,
+}: SettingsRowProps) {
+  return (
+    <div
+      className={["sui-settingsrow", className ?? ""].filter(Boolean).join(" ")}
+    >
+      <div className="sui-settingsrow__text">
+        <span className="sui-settingsrow__label">{label}</span>
+        {description && (
+          <span className="sui-settingsrow__desc">{description}</span>
+        )}
+      </div>
+      <div className="sui-settingsrow__control">{control}</div>
+    </div>
+  );
+}