Various UX improvements and bug fixes

- Fix mustChangePassword session flag for users with pw=NULL
- Add PrF (Private Führung) as new ArtFuehrung type
- Split datetime-local into separate date + TimePicker5 (5-min steps, auto-repeat)
- Responsive Beginn/Ende layout: stacked on mobile, inline on desktop
- Sort BEOs alphabetically by Kürzel in selector
- Title shows active kuppel; hide user display in header
- Selected BEOs show Kürzel only (name stays in dropdown)
- Session timeout reduced to 1 hour
- Add CLAUDE.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/MainClient.tsx

@@ -48,14 +48,11 @@ export default function MainClient({ kuerzel, beoId, beoName }: Props) {
 
         {/* Header */}
         <div className="flex justify-between items-start sm:items-center mb-4 gap-2">
-          <h1 className="text-xl sm:text-3xl font-bold leading-tight">
-            Logbuch<span className="hidden sm:inline"> — Sternwarte Welzheim</span>
+          <h1 className="text-xl sm:text-2xl font-bold leading-tight">
+            <span className="hidden sm:inline">Sternwarte-Welzheim &nbsp; </span>
+            Logbuch für {activeKuppel}-Kuppel
           </h1>
           <div className="flex items-center gap-2 shrink-0">
-            <span className="text-xs sm:text-sm text-gray-600 hidden sm:inline">
-              {kuerzel} — {beoName}
-            </span>
-            <span className="text-xs text-gray-600 sm:hidden">{kuerzel}</span>
             <button
               onClick={handleLogout}
               className="text-xs sm:text-sm px-2 sm:px-3 py-1.5 bg-gray-200 hover:bg-gray-300 rounded-lg text-gray-700"