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/layout/locale-toggle.tsx

@@ -13,8 +13,6 @@ import {
 import { AppLocale, getLocalizedPath, stripLocalePrefix } from "@/lib/locale";
 import { cn } from "@/lib/utils";
 
-const PENDING_TOAST_STORAGE_KEY = "mohfarawati-pending-toast";
-
 type LocaleToggleProps = {
   locale: string;
   defaultLocale: AppLocale;
@@ -22,12 +20,6 @@ type LocaleToggleProps = {
   showLabel?: boolean;
 };
 
-const localeChangedMessages: Record<AppLocale, string> = {
-  de: "Sprache auf Deutsch gewechselt",
-  en: "Language changed to English",
-  ar: "تم تغيير اللغة إلى العربية",
-};
-
 export function LocaleToggle({
   locale,
   defaultLocale,
@@ -85,22 +77,6 @@ export function LocaleToggle({
           >
             <a
               href={getLocalizedPath(targetLocale, currentPath, defaultLocale)}
-              onClick={() => {
-                const message = localeChangedMessages[targetLocale];
-
-                if (!message) {
-                  return;
-                }
-
-                window.sessionStorage.setItem(
-                  PENDING_TOAST_STORAGE_KEY,
-                  JSON.stringify({
-                    type: "success",
-                    message,
-                    targetLocale,
-                  }),
-                );
-              }}
               className="group flex h-10 w-10 items-center justify-center rounded-full"
             >
               <Image