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.stories.tsx

@@ -0,0 +1,82 @@
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { SettingsRow } from "@shared/components/SettingsRow";
+import { ToggleSwitch } from "@shared/components/ToggleSwitch";
+import { Select } from "@shared/components/Select";
+import { Card } from "@shared/components/Card";
+
+const meta: Meta<typeof SettingsRow> = {
+  title: "Primitives/SettingsRow",
+  component: SettingsRow,
+  tags: ["autodocs"],
+  parameters: { layout: "padded" },
+  decorators: [
+    (S) => (
+      <div style={{ maxWidth: "24rem" }}>
+        <S />
+      </div>
+    ),
+  ],
+};
+export default meta;
+type Story = StoryObj<typeof SettingsRow>;
+
+export const Toggle: Story = {
+  args: {
+    label: "Auto-classify",
+    control: <ToggleSwitch checked onChange={() => {}} size="sm" />,
+  },
+};
+
+export const WithDescription: Story = {
+  args: {
+    label: "Detect PII",
+    description: "Scan documents for sensitive fields on save",
+    control: <ToggleSwitch checked onChange={() => {}} size="sm" />,
+  },
+};
+
+/** A settings list inside a padding-none Card. */
+export const List: Story = {
+  render: () => (
+    <Card padding="none">
+      {[
+        { label: "Auto-classify", on: true },
+        { label: "Extract tables", on: true },
+        { label: "Strip blank pages", on: false },
+      ].map((r, i) => (
+        <div
+          key={r.label}
+          style={{
+            padding: "0.7rem 0.875rem",
+            borderTop: i > 0 ? "1px solid var(--color-border)" : undefined,
+          }}
+        >
+          <SettingsRow
+            label={r.label}
+            control={
+              <ToggleSwitch checked={r.on} onChange={() => {}} size="sm" />
+            }
+          />
+        </div>
+      ))}
+    </Card>
+  ),
+};
+
+export const SelectControl: Story = {
+  args: {
+    label: "OCR level",
+    control: (
+      <Select
+        inputSize="sm"
+        value="high"
+        onChange={() => {}}
+        options={[
+          { value: "standard", label: "Standard" },
+          { value: "high", label: "High" },
+          { value: "max", label: "Maximum" },
+        ]}
+      />
+    ),
+  },
+};