feat: Implement Event Deep-Linking (?event=ID) and TEILEN share link buttons

frontend/src/pages/HomePage.jsx

@@ -1,7 +1,7 @@
 /* Hallmark · pre-emit critique: P5 H5 E5 S5 R5 V5 */
 /* Hallmark · redesign: HomePage · studied-DNA: https://inihaus.de · macrostructure: Newsstand Feed */
 import React, { useState } from 'react';
-import { Search, Calendar, MapPin, Clock, ArrowRight, Plus, EyeOff, CheckCircle2, Edit3, ShieldAlert, Trash2 } from 'lucide-react';
+import { Search, Calendar, MapPin, Clock, ArrowRight, Plus, EyeOff, CheckCircle2, Edit3, ShieldAlert, Trash2, Share2 } from 'lucide-react';
 
 export default function HomePage({
   events,
@@ -9,6 +9,7 @@ export default function HomePage({
   onSelectEvent,
   onOpenCreateEvent,
   onToggleEventActive,
+  onShareEvent,
   onEditEvent,
   onDeleteEvent,
   branding
@@ -190,6 +191,16 @@ export default function HomePage({
                           Schichtplan <ArrowRight className="w-3.5 h-3.5" />
                         </button>
 
+                        {onShareEvent && (
+                          <button
+                            onClick={() => onShareEvent(evt)}
+                            className="py-1.5 px-2.5 rounded-sm text-[10px] font-mono font-bold bg-blue-500/10 text-blue-400 border border-blue-500/20 hover:bg-blue-500/20 transition flex items-center gap-1 shrink-0"
+                            title="Direktlink zu dieser Veranstaltung kopieren"
+                          >
+                            <Share2 className="w-3.5 h-3.5" /> TEILEN
+                          </button>
+                        )}
+
                         {canManage && onEditEvent && (
                           <button
                             onClick={() => onEditEvent(evt)}