Portal (#6391)

# Description of Changes

## What & why

This PR introduces the **Stirling developer portal** — a new
control-plane frontend that sits alongside the existing PDF editor —
plus the shared design system and workspace structure needed to host
both apps in one frontend.

The portal is the parent product surface: where users connect sources,
compose pipelines, wire agents, and manage usage / billing /
infrastructure, with the PDF editor as one capability inside it. This PR
lays the **foundation** — workspace reshape, design system, app shell,
navigation, and a mock-driven home — rather than wiring real backends
(those surfaces are placeholders for follow-up phases).

## What's in this PR

**1. Frontend repo reshape (`frontend/src/` → `frontend/editor/`)**
The existing editor app moved under `frontend/editor/`, so `editor`,
`portal`, and `shared` are siblings in one workspace. All references
were updated accordingly: `LICENSE`, `.dockerignore`, `.gitignore`,
build/sign shell scripts, the GH language-check script, the Taskfile,
and Docker config. **No editor source logic changed — path references
only.**

**2. New shared design system (`frontend/shared/`)**
- **Design tokens** in `tokens.css` as the single runtime source of
truth (light/dark, category accents, gradients). `tokens.ts` now holds
only the `Tier` type — the old JS palette mirror was removed (nothing
consumed it and it had drifted).
- ~30 framework-light **components** (Card, Button, Input, Select, Tabs,
Modal, Drawer, Toast, MetricCard, StatusBadge, Skeleton, EmptyState, …)
with Storybook stories.
- **Typed data catalogues**: `endpoints.ts` (10 verticals / 64
endpoints) and `ops.ts`.

**3. New developer portal app (`frontend/portal/`)**
- App shell: `Header`, `Sidebar`, `AssistantPanel`, search modal,
notifications, tier switcher, theme toggle, MSW toggle.
- **Tier-aware** home (free / pay-as-you-go / enterprise): KPI strip,
30-day usage chart, onboarding checklist, quick actions, recent
activity, region health, product grid, and a curated **"Popular use
cases"** teaser.
- **Documents** view hosting the full, tab-filterable endpoint
catalogue.
- Placeholder views for Sources / Pipelines / Agents / Editor /
Infrastructure / Usage & Billing / Developer Docs / Settings (follow-up
phases).
- **MSW-mocked** API layer: `api/*` issues real `fetch`, intercepted by
mocks in dev/Storybook; pointing at a real backend is just a matter of
not registering MSW. `react-router` URLs; Tier / View / UI contexts.

**4. Tooling & guardrails**
- ESLint extended to `portal` + `shared`, with **layering-boundary
rules**: `shared/` may depend only on third-party packages and itself
(no `@app` / `@portal` / `@core` / `@proprietary` / Tauri), so it stays
cleanly extractable into a standalone package later.
- `dpdm` circular-dependency check now walks editor + portal + shared
(the old glob matched only 2 files).
- New **devDependencies only** — Storybook (+ a11y/docs/themes addons),
MSW. No runtime dependencies added.
- New tasks: `frontend:dev:portal`, `frontend:build:portal`.

## Testing done locally

- `tsc` for both `portal` and `shared` projects — clean
- `eslint --max-warnings=0` across the whole frontend — clean
- `dpdm` circular-dependency check — no cycles
- Editor builds clean: `vite build editor --mode core` (✓ built, only
the pre-existing >500 kB chunk-size advisory)
- Editor runs in dev (core mode) with **zero console errors**; portal
runs in dev across all three tiers

## Notes for reviewers

- The change is overwhelmingly **additive**: `shared/` and `portal/` are
brand-new; the existing editor is path-reference changes only.
- The portal is intentionally **mock-driven** at this stage — real
backends and the remaining views land in follow-up phases.

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have run `task check` to verify linters, typechecks, and tests
pass
- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

---------

Co-authored-by: Claude Opus 4.8 (1M context) <[email protected]>

frontend/shared/components/FormField.tsx

@@ -0,0 +1,79 @@
+import {
+  cloneElement,
+  isValidElement,
+  useId,
+  type ReactElement,
+  type ReactNode,
+} from "react";
+import "@shared/components/FormField.css";
+
+export interface FormFieldProps {
+  label?: ReactNode;
+  /** Helper text shown under the control. Replaced by `error` when present. */
+  helperText?: ReactNode;
+  /** Error string. Causes the control + helper region to swap to the error tone. */
+  error?: ReactNode;
+  required?: boolean;
+  /** A single form control as a React element. Receives id + aria-* props. */
+  children: ReactElement<{
+    id?: string;
+    "aria-invalid"?: boolean;
+    "aria-describedby"?: string;
+    required?: boolean;
+  }>;
+  className?: string;
+}
+
+/**
+ * Standardised label + control + helper/error wrapper. Works with the bare
+ * native controls in this design system (Input, Select, Checkbox, Radio,
+ * Slider) or with any third-party control that accepts `id` + `aria-*`.
+ */
+export function FormField({
+  label,
+  helperText,
+  error,
+  required,
+  children,
+  className,
+}: FormFieldProps) {
+  const autoId = useId();
+  if (!isValidElement(children)) {
+    throw new Error("FormField requires exactly one React element child");
+  }
+  const controlId = children.props.id ?? autoId;
+  const describedById = error || helperText ? `${controlId}-help` : undefined;
+
+  const child = cloneElement(children, {
+    id: controlId,
+    "aria-invalid": error ? true : undefined,
+    "aria-describedby": describedById,
+    required: required ?? children.props.required,
+  });
+
+  return (
+    <div
+      className={["sui-field", error ? "sui-field--error" : "", className ?? ""]
+        .filter(Boolean)
+        .join(" ")}
+    >
+      {label && (
+        <label htmlFor={controlId} className="sui-field__label">
+          {label}
+          {required && (
+            <span className="sui-field__required" aria-hidden>
+              {" "}
+              *
+            </span>
+          )}
+        </label>
+      )}
+      <div className="sui-field__control">{child}</div>
+      {(error || helperText) && (
+        <div id={describedById} className="sui-field__help">
+          {error ?? helperText}
+        </div>
+      )}
+    </div>
+  );
+}