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>

create_table.sql

@@ -11,7 +11,7 @@ CREATE TABLE objekte (
 CREATE TABLE logbuch (
   ID INT AUTO_INCREMENT PRIMARY KEY,
   Kuppel ENUM('West','Ost','Süd','Pluto') NOT NULL DEFAULT 'West',
-  ArtFuehrung ENUM('RF','SF','BEOS','SonF','TD','Beob','ToT','Sonst') NOT NULL DEFAULT 'RF',
+  ArtFuehrung ENUM('RF','SF','PrF','BEOS','SonF','TD','Beob','ToT','Sonst') NOT NULL DEFAULT 'RF',
   Beginn DATETIME NOT NULL,
   Ende DATETIME NOT NULL,
   Besucher INT DEFAULT 0,