refactor: drop toast + over-engineered extras, add inline admin feedback

Phase 1 cleanup of the personal-site revamp. Backend/architecture untouched;
changes are limited to removing unused complexity and restoring feedback.

Removals
- Toast system: delete react-hot-toast, Toaster, QueryToastBridge, lib/toast,
  the toggle/easter-egg calls, related i18n keys and the dependency.
- Contact protection: remove Turnstile + per-IP rate limiting
  (lib/contact-guard, lib/contact-protection, admin screen, form widget,
  app-config wiring, nav entry, test).
- Speculative specs: delete orders, products, downloads, project-inquiry.

Inline feedback (replaces toast, no new deps)
- Add lib/admin-feedback (withFlash/readFlash) and components/admin/admin-flash,
  rendered centrally by AdminDashboardShell.
- Emit success/error messages for media, site-settings, portfolio, smtp,
  marquee and maintenance actions; pages read them via searchParams.
- Contact form shows validation/delivery errors inline; success still
  redirects to /success.

Docs
- Fix stale paths in frontend-system-* (components/root -> components/admin,
  lib/root-navigation -> lib/admin-navigation, drop phantom src/) and remove
  contact-protection references from docs and CLAUDE.md.
- Add docs/PHASE0_DIAGNOSIS.md (diagnosis report).

Note: proxy.ts self-fetch kept intentionally; it also drives maintenance mode.

components/ui/toaster.tsx

@@ -1,32 +0,0 @@
-"use client";
-
-import { Toaster as HotToaster, type ToasterProps } from "react-hot-toast";
-
-type AppToasterProps = ToasterProps & {
-  locale: string;
-};
-
-export function Toaster({ locale, ...props }: AppToasterProps) {
-  const isArabic = locale === "ar";
-
-  const toastClassName = `${isArabic ? "font-arabic tracking-normal" : "font-latin"} text-[13px] leading-5`;
-
-  return (
-    <HotToaster
-      key={locale}
-      {...props}
-      position={props.position ?? (isArabic ? "top-right" : "top-left")}
-      reverseOrder={props.reverseOrder ?? false}
-      toastOptions={{
-        ...props.toastOptions,
-        className:
-          props.toastOptions?.className ??
-          toastClassName,
-        style: {
-          borderRadius: "36px",
-          ...(props.toastOptions?.style ?? {}),
-        },
-      }}
-    />
-  );
-}