docs: mark df-admin-interface as Laravel 13-transparent

LARAVEL_13_COMPAT.md

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+# Laravel 13 Compatibility Notes
+
+This repo is the **Angular 16 admin UI** for DreamFactory. It is a frontend-only
+package and has no PHP / Laravel runtime dependency. As part of the
+DreamFactory Laravel 11 -> 13 upgrade campaign (Waves 0-5), this package was
+audited for compatibility against the L13 backend.
+
+## Audit result: L13-transparent
+
+**No code changes are required for the UI to function against the Laravel 13
+backend.** This document captures why, so future contributors don't need to
+re-derive it.
+
+### What was audited
+
+1. **API endpoints** consumed by the UI (`src/app/shared/constants/urls.ts`
+   and call sites grepped under `src/`). All paths live under `/api/v2/...`
+   and are served by `df-core` / `df-user` / `df-system`, which are upgraded
+   to L13 as composer-only bumps with no route or contract changes.
+2. **Auth endpoints**: `/api/v2/system/admin/session`, `/api/v2/user/session`,
+   `/api/v2/system/admin/password`, `/api/v2/user/password`,
+   `/api/v2/user/register`. All unchanged.
+3. **Error envelope**: the UI's HTTP interceptors
+   (`src/app/shared/interceptors/error.interceptor.ts`,
+   `src/app/shared/interceptors/snackbar.interceptor.ts`) and many feature
+   components consume DreamFactory's custom error envelope:
+   ```json
+   { "error": { "message": "...", "code": 400, "context": { ... } } }
+   ```
+   This envelope is produced by `df-core`'s exception handler, **not** by
+   Laravel's default JSON error formatter. Default-Laravel JSON error shape
+   changes between L11 and L13 (`message` / `exception` / `file` keys) do not
+   reach this UI.
+4. **Composer coupling**: `composer.json` declares only
+   `dreamfactory/installer: *`, a Composer installer plugin that stages the
+   built `dist/` artifact into the host app's public dir. There is no
+   Laravel framework dependency here.
+
+### What was NOT audited (out of scope)
+
+- **Angular 16 modernization**: Angular 16 reached end-of-life in November
+  2024. The UI will continue to function against L13, but Angular itself
+  should be modernized in a separate track (Angular 17 / 18 / 19), decoupled
+  from the L13 upgrade.
+- **Backend-driven UI features** (e.g., new admin screens for L13-specific
+  features): none are planned for the L13 upgrade — Waves 0-5 are mechanical
+  framework bumps, not feature work.
+
+## Campaign tracking
+
+This package is recorded in the campaign as **L13-transparent: docs-only
+alignment PR**. See the corresponding shift/laravel-13 PRs in sibling
+DreamFactory packages for the broader upgrade context.