Redesign PlatformPlatform landing page with minimalistic approach (#791)

### Summary & Motivation

Redesign the landing page with a minimalistic approach to provide a
cleaner, more professional first impression. The previous landing page
contained multiple feature sections, community content, and technology
showcases that were removed in favor of a simple welcome message
encouraging users to customize the page with their own branding.

- Remove all feature sections, community section, technology sections,
and CTA sections (10 component files deleted)
- Create new reusable `PublicNavigation` and `PublicFooter` components
for consistent public-facing pages
- Add support for routes to opt out of `AuthSyncModal` via
`disableAuthSync` context flag
- Fix tenant switching to preserve the current path after navigation
(important for landing page experience)
- Change login/signup layout breakpoint from `md` to `lg` for better
responsive behavior
- Update footer attribution to "Built with PlatformPlatform" with HTML
comment

The new landing page displays a welcome message, navigation with
login/signup buttons, theme/locale switchers, and a footer with social
links. This provides a minimal starting point that downstream projects
can easily customize.

### Checklist

- [x] I have added tests, or done manual regression tests
- [x] I have updated the documentation, if necessary

Author: tjementum

application/account-management/WebApp/federated-modules/common/TenantSelector.tsx

@@ -1,6 +1,7 @@
 import { t } from "@lingui/core/macro";
 import { Trans } from "@lingui/react/macro";
 import type { UserInfo } from "@repo/infrastructure/auth/AuthenticationProvider";
+import { loggedInPath } from "@repo/infrastructure/auth/constants";
 import { useUserInfo } from "@repo/infrastructure/auth/hooks";
 import { Badge } from "@repo/ui/components/Badge";
 import { Button } from "@repo/ui/components/Button";
@@ -270,11 +271,10 @@ export default function TenantSelector({ onShowInvitationDialog, variant = "defa
       setIsSwitching(true);
     },
     onSuccess: () => {
-      // Keep the loader visible briefly before redirecting
+      // Stay on the same path, but default to loggedInPath if on root
       // Don't set isSwitching to false here - let the redirect handle it
-      setTimeout(() => {
-        window.location.href = "/";
-      }, 250);
+      const targetPath = window.location.pathname === "/" ? loggedInPath : window.location.pathname;
+      window.location.href = targetPath;
     },
     onError: () => {
       // Hide the loader on error

application/account-management/WebApp/federated-modules/sideMenu/FederatedSideMenu.tsx

@@ -1,4 +1,5 @@
 import { t } from "@lingui/core/macro";
+import { loggedInPath } from "@repo/infrastructure/auth/constants";
 import { useUserInfo } from "@repo/infrastructure/auth/hooks";
 import { SideMenu } from "@repo/ui/components/SideMenu";
 import { useState } from "react";
@@ -30,10 +31,9 @@ export default function FederatedSideMenu({ currentSystem }: Readonly<FederatedS
       setIsSwitching(true);
     },
     onSuccess: () => {
-      // Keep the loader visible briefly before redirecting
-      setTimeout(() => {
-        window.location.href = "/";
-      }, 250);
+      // Stay on the same path, but default to loggedInPath if on root
+      const targetPath = globalThis.location.pathname === "/" ? loggedInPath : globalThis.location.pathname;
+      globalThis.location.href = targetPath;
     },
     onError: () => {
       setIsSwitching(false);