fix: resolve code quality issues and add missing i18n keys (#162, #163)

Add missing i18n translations for hero image focal point picker in both
EN and DE locales. Fix lint errors across touched files: remove unused
imports/variables, replace raw buttons with shared Button component,
eliminate inline styles, extract duplicated backend validation, and
remove dead heroImagePosition type.

backend/src/routes/adminEvents.js

@@ -1,5 +1,5 @@
 const express = require('express');
-const { body, query, validationResult } = require('express-validator');
+const { body, validationResult } = require('express-validator');
 const { db, logActivity } = require('../database/db');
 const { formatBoolean } = require('../utils/dbCompat');
 const { adminAuth } = require('../middleware/auth');
@@ -17,10 +17,20 @@ const { escapeLikePattern } = require('../utils/sqlSecurity');
 const { validatePasswordInContext, getBcryptRounds } = require('../utils/passwordValidation');
 const logger = require('../utils/logger');
 const { buildShareLinkVariants } = require('../services/shareLinkService');
-const { parseBooleanInput, parseStringInput, parseJsonInput } = require('../utils/parsers');
+const { parseBooleanInput, parseStringInput } = require('../utils/parsers');
 const eventTypeService = require('../services/eventTypeService');
 const { validateFileType } = require('../utils/fileSecurityUtils');
 
+// Shared validator for hero_image_anchor – accepts legacy keywords or "X% Y%" focal point
+const validateHeroImageAnchor = (value) => {
+  if (['top', 'center', 'bottom'].includes(value)) return true;
+  if (typeof value === 'string' && /^\d{1,3}%\s+\d{1,3}%$/.test(value)) {
+    const [x, y] = value.split(/\s+/).map(v => parseInt(v));
+    if (x >= 0 && x <= 100 && y >= 0 && y <= 100) return true;
+  }
+  throw new Error('Must be top, center, bottom, or "X% Y%" (0-100)');
+};
+
 // Get storage path from environment or default
 const getStoragePath = () => process.env.STORAGE_PATH || path.join(__dirname, '../../../storage');
 
@@ -198,14 +208,7 @@ router.post('/', adminAuth, requirePermission('events.create'), [
   body('header_style').optional().isIn(['hero', 'standard', 'minimal', 'none']),
   body('hero_divider_style').optional().isIn(['wave', 'straight', 'angle', 'curve', 'none']),
   // Hero image anchor position (#162) – accepts legacy keywords or "X% Y%" focal point
-  body('hero_image_anchor').optional().custom((value) => {
-    if (['top', 'center', 'bottom'].includes(value)) return true;
-    if (typeof value === 'string' && /^\d{1,3}%\s+\d{1,3}%$/.test(value)) {
-      const [x, y] = value.split(/\s+/).map(v => parseInt(v));
-      if (x >= 0 && x <= 100 && y >= 0 && y <= 100) return true;
-    }
-    throw new Error('Must be top, center, bottom, or "X% Y%" (0-100)');
-  })
+  body('hero_image_anchor').optional().custom(validateHeroImageAnchor)
 ], async (req, res) => {
   try {
     logger.debug('Create event request body', { body: req.body });
@@ -313,10 +316,6 @@ router.post('/', adminAuth, requirePermission('events.create'), [
       }
     }
     
-    // Get event type info for slug generation
-    const eventTypeInfo = await eventTypeService.getEventTypeForSlug(event_type);
-    const slugPrefix = eventTypeInfo.slug_prefix || event_type;
-
     // Generate unique slug
     const processedEventName = event_name
       .toLowerCase()
@@ -337,7 +336,7 @@ router.post('/', adminAuth, requirePermission('events.create'), [
     
     // Generate share link respecting configured format
     const shareToken = crypto.randomBytes(16).toString('hex');
-    const { sharePath, shareUrl, shareLinkToStore } = await buildShareLinkVariants({ slug, shareToken });
+    const { shareUrl, shareLinkToStore } = await buildShareLinkVariants({ slug, shareToken });
     
     // Hash password with configurable rounds (random placeholder when not required)
     const password_hash = requirePassword
@@ -665,7 +664,7 @@ router.put('/:id', adminAuth, requirePermission('events.edit'), [
   body('overlay_protection').optional().isBoolean(),
   body('image_quality').optional().isInt({ min: 1, max: 100 }),
   body('fragmentation_level').optional().isInt({ min: 1, max: 10 }),
-  body('password').optional().isString().custom((value, { req }) => {
+  body('password').optional().isString().custom((value) => {
     if (value === undefined || value === null || value === '') {
       return true;
     }
@@ -683,14 +682,7 @@ router.put('/:id', adminAuth, requirePermission('events.edit'), [
   body('header_style').optional().isIn(['hero', 'standard', 'minimal', 'none']),
   body('hero_divider_style').optional().isIn(['wave', 'straight', 'angle', 'curve', 'none']),
   // Hero image anchor position (#162) – accepts legacy keywords or "X% Y%" focal point
-  body('hero_image_anchor').optional().custom((value) => {
-    if (['top', 'center', 'bottom'].includes(value)) return true;
-    if (typeof value === 'string' && /^\d{1,3}%\s+\d{1,3}%$/.test(value)) {
-      const [x, y] = value.split(/\s+/).map(v => parseInt(v));
-      if (x >= 0 && x <= 100 && y >= 0 && y <= 100) return true;
-    }
-    throw new Error('Must be top, center, bottom, or "X% Y%" (0-100)');
-  })
+  body('hero_image_anchor').optional().custom(validateHeroImageAnchor)
 ], async (req, res) => {
   try {
     const errors = validationResult(req);

backend/src/routes/gallery.js

@@ -795,7 +795,7 @@ router.get('/:slug/photo/:photoId',
 
         if (range) {
           // Parse range header
-          const parts = range.replace(/bytes=/, "").split("-");
+          const parts = range.replace(/bytes=/, '').split('-');
           const start = parseInt(parts[0], 10);
           const end = parts[1] ? parseInt(parts[1], 10) : fileSize - 1;
           const chunksize = (end - start) + 1;