test: add browser-based unit tests for helpers, i18n, router

AGENTS.md

@@ -29,6 +29,9 @@ python3 -m http.server 8080
 # Oder mit Live-Reload
 npx live-server
 
+# Tests ausführen (im Browser)
+# Server starten, dann http://localhost:8080/tests/ öffnen
+
 # Git Push (Token in URL)
 git push origin master
 ```
@@ -54,7 +57,6 @@ js/
 │   ├── categories.js   # Kategorien Service (Baum, Übersetzungen)
 │   ├── locations.js    # Standorte Service (Geo-Suche)
 │   ├── conversations.js # Zero-Knowledge Chat (E2E verschlüsselt)
-│   ├── chat.js         # LocalStorage Chat (Legacy/Mock)
 │   ├── crypto.js       # NaCl Encryption
 │   ├── currency.js     # XMR/Fiat Umrechnung
 │   └── pow-captcha.js  # Proof-of-Work Captcha (Challenge/Verify)
@@ -81,6 +83,13 @@ css/
 assets/
 └── fonts/              # Self-hosted Fonts (Inter, Space Grotesk)
 
+tests/
+├── index.html          # Test-Runner UI (im Browser öffnen)
+├── test-runner.js      # Minimaler Test-Framework
+├── helpers.test.js     # Unit Tests für helpers.js
+├── i18n.test.js        # Unit Tests für i18n.js
+└── router.test.js      # Unit Tests für router.js
+
 locales/
 ├── de.json             # Deutsch (Fallback)
 ├── en.json