feat(help): in-app help center with per-screen guides and pictures

A help icon on every screen opens a panel with the screen's overview, its
sub-screens, task guides with a framed picture per step, search across guides
and the wiki, and a switch to any other screen's help. Guides exist for the
dashboard, Vacay, Atlas, Collections, Journey (list, journal, studio), Settings
(all tabs), Admin (all tabs) and the trip frame; the trip's own screens are
in progress. Pictures are produced by Playwright (client/e2e/help), texts in
all 23 languages.

client/src/components/Help/HelpDocLink.tsx

@@ -0,0 +1,27 @@
+import React from 'react'
+import { Link } from 'react-router'
+import { FileText, ArrowUpRight } from 'lucide-react'
+import { useHelpStore } from '../../store/helpStore'
+
+/**
+ * A row that leads into the full Help & Docs page. The panel closes on the
+ * way: the docs page has its own navigation and the two side by side would
+ * fight for the width.
+ */
+export default function HelpDocLink({ to, title, subtitle }: { to: string; title: string; subtitle?: string }): React.ReactElement {
+  const closeHelp = useHelpStore(s => s.closeHelp)
+  return (
+    <Link
+      to={to}
+      onClick={closeHelp}
+      className="group flex items-center gap-2.5 rounded-lg px-2 py-1.5 -mx-2 hover:bg-surface-hover transition-colors"
+    >
+      <FileText className="w-4 h-4 text-content-faint flex-shrink-0" />
+      <span className="min-w-0 flex-1">
+        <span className="block text-body text-content-secondary group-hover:text-content truncate transition-colors">{title}</span>
+        {subtitle && <span className="block text-caption text-content-faint truncate">{subtitle}</span>}
+      </span>
+      <ArrowUpRight className="w-3.5 h-3.5 text-content-faint opacity-0 group-hover:opacity-100 transition-opacity flex-shrink-0" />
+    </Link>
+  )
+}