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/IconBadge.stories.tsx

@@ -0,0 +1,42 @@
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { IconBadge } from "@shared/components/IconBadge";
+
+function Glyph() {
+  return (
+    <svg viewBox="0 0 24 24" width={16} height={16} fill="currentColor">
+      <rect x="3" y="4" width="18" height="4" rx="1" />
+      <rect x="3" y="10" width="18" height="4" rx="1" />
+      <rect x="3" y="16" width="18" height="4" rx="1" />
+    </svg>
+  );
+}
+
+const meta: Meta<typeof IconBadge> = {
+  title: "Primitives/IconBadge",
+  component: IconBadge,
+  tags: ["autodocs"],
+  parameters: { layout: "centered" },
+  args: { accent: "blue", size: "md", children: <Glyph /> },
+  argTypes: {
+    accent: {
+      control: "inline-radio",
+      options: ["blue", "purple", "green", "amber", "red"],
+    },
+    size: { control: "inline-radio", options: ["sm", "md"] },
+  },
+};
+export default meta;
+type Story = StoryObj<typeof IconBadge>;
+
+export const Blue: Story = {};
+export const Accents: Story = {
+  render: () => (
+    <div style={{ display: "flex", gap: 12 }}>
+      {(["blue", "purple", "green", "amber", "red"] as const).map((a) => (
+        <IconBadge key={a} accent={a}>
+          <Glyph />
+        </IconBadge>
+      ))}
+    </div>
+  ),
+};