fix: relax password requirements and improve password UI

- Reduce minimum password length from 12 to 8 characters
- Make special characters optional for gallery passwords
- Lower strength requirement from score 3 to 1 for galleries
- Add eye icon toggle for password visibility on each field
- Remove redundant 'Show passwords' checkbox
- Add translation for password security requirements error
- Update both English and German translations

This allows users to use simpler passwords like 'Sommer2025\!' for events
while maintaining security through other measures like expiration dates.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/src/i18n/locales/de.json

@@ -872,6 +872,7 @@
     "passwordRequired": "Passwort ist erforderlich",
     "passwordMinLength": "Passwort muss mindestens 6 Zeichen lang sein",
     "passwordsDoNotMatch": "Passwörter stimmen nicht überein",
+    "passwordSecurityRequirements": "Passwort erfüllt nicht die Sicherheitsanforderungen",
     "expirationRange": "Ablauf muss zwischen 1 und 365 Tagen liegen"
   },
   "maintenance": {