feat: Add German translation support for MinIO WebUI

- Set up i18n infrastructure with react-i18next
- Add German as default language with English fallback
- Create comprehensive translation files for all UI components
- Translate Dashboard, QuickStartWizard, Reports, and navigation
- Add language switcher in app header
- Maintain existing German email template in backend
- Create modular translation structure with namespaces
- Add testing checklist and implementation summary

All user-facing strings in dashboard, quick wizard, and reports
sections are now available in German, fulfilling the requirement
for complete German localization.

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

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

frontend/package-lock.json

@@ -21,10 +21,13 @@
         "axios": "^1.6.5",
         "chart.js": "^4.4.1",
         "date-fns": "^3.2.0",
+        "i18next": "^25.3.2",
+        "i18next-browser-languagedetector": "^8.2.0",
         "react": "^18.2.0",
         "react-chartjs-2": "^5.2.0",
         "react-dom": "^18.2.0",
         "react-hook-form": "^7.48.2",
+        "react-i18next": "^15.6.1",
         "react-router-dom": "^6.21.1",
         "react-scripts": "5.0.1",
         "typescript": "^5.3.3",
@@ -10165,6 +10168,15 @@
         "node": ">=12"
       }
     },
+    "node_modules/html-parse-stringify": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/html-parse-stringify/-/html-parse-stringify-3.0.1.tgz",
+      "integrity": "sha512-KknJ50kTInJ7qIScF3jeaFRpMpE8/lfiTdzf/twXyPBLAGrLRTmkz3AdTnKeh40X8k9L2fdYwEp/42WGXIRGcg==",
+      "license": "MIT",
+      "dependencies": {
+        "void-elements": "3.1.0"
+      }
+    },
     "node_modules/html-webpack-plugin": {
       "version": "5.6.3",
       "resolved": "https://registry.npmjs.org/html-webpack-plugin/-/html-webpack-plugin-5.6.3.tgz",
@@ -10318,6 +10330,46 @@
         "node": ">=10.17.0"
       }
     },
+    "node_modules/i18next": {
+      "version": "25.3.2",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-25.3.2.tgz",
+      "integrity": "sha512-JSnbZDxRVbphc5jiptxr3o2zocy5dEqpVm9qCGdJwRNO+9saUJS0/u4LnM/13C23fUEWxAylPqKU/NpMV/IjqA==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://locize.com"
+        },
+        {
+          "type": "individual",
+          "url": "https://locize.com/i18next.html"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.i18next.com/how-to/faq#i18next-is-awesome.-how-can-i-support-the-project"
+        }
+      ],
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.27.6"
+      },
+      "peerDependencies": {
+        "typescript": "^5"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/i18next-browser-languagedetector": {
+      "version": "8.2.0",
+      "resolved": "https://registry.npmjs.org/i18next-browser-languagedetector/-/i18next-browser-languagedetector-8.2.0.tgz",
+      "integrity": "sha512-P+3zEKLnOF0qmiesW383vsLdtQVyKtCNA9cjSoKCppTKPQVfKd2W8hbVo5ZhNJKDqeM7BOcvNoKJOjpHh4Js9g==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.23.2"
+      }
+    },
     "node_modules/iconv-lite": {
       "version": "0.6.3",
       "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.6.3.tgz",
@@ -15220,6 +15272,32 @@
         "react": "^16.8.0 || ^17 || ^18 || ^19"
       }
     },
+    "node_modules/react-i18next": {
+      "version": "15.6.1",
+      "resolved": "https://registry.npmjs.org/react-i18next/-/react-i18next-15.6.1.tgz",
+      "integrity": "sha512-uGrzSsOUUe2sDBG/+FJq2J1MM+Y4368/QW8OLEKSFvnDflHBbZhSd1u3UkW0Z06rMhZmnB/AQrhCpYfE5/5XNg==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.27.6",
+        "html-parse-stringify": "^3.0.1"
+      },
+      "peerDependencies": {
+        "i18next": ">= 23.2.3",
+        "react": ">= 16.8.0",
+        "typescript": "^5"
+      },
+      "peerDependenciesMeta": {
+        "react-dom": {
+          "optional": true
+        },
+        "react-native": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/react-is": {
       "version": "19.1.0",
       "resolved": "https://registry.npmjs.org/react-is/-/react-is-19.1.0.tgz",
@@ -18030,6 +18108,15 @@
         "node": ">= 0.8"
       }
     },
+    "node_modules/void-elements": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/void-elements/-/void-elements-3.1.0.tgz",
+      "integrity": "sha512-Dhxzh5HZuiHQhbvTW9AMetFfBHDMYpo23Uo9btPXgdYP+3T5S+p+jgNy7spra+veYhBP2dCSgxR/i2Y02h5/6w==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/w3c-hr-time": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/w3c-hr-time/-/w3c-hr-time-1.0.2.tgz",