Delete e-mails from the Postfach; searchable assignment picker

Each Postfach e-mail gets a Delete button (POST /postfach/:id/delete),
which also removes stored attachment files. The plain assignment
dropdown is replaced by a searchable combobox that filters applications
by company, position and city, with keyboard navigation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server.js

@@ -1341,6 +1341,23 @@ initializeDatabase().then(() => {
     }
   });
 
+  // Delete an e-mail from the Postfach (removes its stored attachment files too).
+  app.post('/postfach/:emailId/delete', async (req, res) => {
+    try {
+      const emailId = req.params.emailId;
+      const atts = await dbAll('SELECT pfad FROM email_anhaenge WHERE email_id = ?', [emailId]);
+      for (const a of atts) {
+        fs.promises.unlink(path.join(emailAnhaengeDir, a.pfad)).catch(() => {});
+      }
+      await dbRun('DELETE FROM email_anhaenge WHERE email_id = ?', [emailId]);
+      await dbRun('DELETE FROM emails WHERE id = ?', [emailId]);
+      res.redirect('/postfach?mailok=' + encodeURIComponent('E-Mail wurde gelöscht.'));
+    } catch (error) {
+      console.error('Error deleting e-mail:', error);
+      res.redirect('/postfach?mailerror=' + encodeURIComponent('Löschen fehlgeschlagen: ' + (error.message || 'Unbekannter Fehler')));
+    }
+  });
+
   // Count of unlinked e-mails — drives the header badge on every page.
   app.get('/api/emails/unassigned-count', async (req, res) => {
     try {