Add 6 new tools: Hasher, Base64, JWT Decoder, Password Gen, Timestamp, Text Diff

- backend/tools/hasher.py: POST /api/hash/sha256 and /api/hash/bcrypt (bcrypt added to requirements)
- backend/tools/base64tool.py: POST /api/base64/encode and /api/base64/decode
- backend/tools/jwtdecoder.py: POST /api/jwt/decode (signature verification disabled)
- backend/tools/passwordgen.py: POST /api/password/generate with charset and length options
- backend/tools/timestamp.py: POST /api/timestamp/convert (unix<->date, ISO 8601 + German format)
- backend/tools/textdiff.py: POST /api/text/diff returning structured added/removed/unchanged lines
- All blueprints registered in app.py and tools/__init__.py
- React components with copy button, dark/light mode support via CSS variables
- ToolOverview rebuilt as card grid; App.jsx routes added for all tools

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/ToolOverview.jsx

@@ -2,9 +2,18 @@ import { useNavigate } from 'react-router-dom';
 import { useEffect, useState } from 'react';
 import axios from '../services/api';
 
+const TOOLS = [
+  { icon: '🔒', path: '/tools/md5',       title: 'MD5 Hasher',           desc: 'MD5-Hash berechnen (nur zur Analyse)' },
+  { icon: '#️⃣', path: '/tools/hasher',    title: 'SHA256 / bcrypt',      desc: 'Sichere Hash-Algorithmen für Strings' },
+  { icon: '📦', path: '/tools/base64',    title: 'Base64',               desc: 'Text kodieren und dekodieren' },
+  { icon: '🔑', path: '/tools/jwt',       title: 'JWT Decoder',          desc: 'JWT Token analysieren (ohne Signaturprüfung)' },
+  { icon: '🔐', path: '/tools/password',  title: 'Passwort-Generator',   desc: 'Sichere Passwörter generieren' },
+  { icon: '🕐', path: '/tools/timestamp', title: 'Timestamp Converter',  desc: 'Unix Timestamp in Datum umrechnen' },
+  { icon: '📝', path: '/tools/textdiff',  title: 'Text Diff',            desc: 'Zwei Texte vergleichen' },
+];
+
 function ToolOverview() {
   const navigate = useNavigate();
-  const role = localStorage.getItem('role');
   const [websites, setWebsites] = useState([]);
   const [loadingWebsites, setLoadingWebsites] = useState(true);
 
@@ -13,7 +22,7 @@ function ToolOverview() {
       try {
         const res = await axios.get('/api/websites');
         setWebsites(res.data);
-      } catch (e) {
+      } catch {
         setWebsites([]);
       } finally {
         setLoadingWebsites(false);
@@ -27,9 +36,24 @@ function ToolOverview() {
       <h2>Tool-Übersicht</h2>
       <p>Wähle ein Tool aus:</p>
 
-      <button onClick={() => navigate('/tools/md5')}>🔒 MD5 Tool</button><br /><br />
+      <div className="card-grid">
+        {TOOLS.map((tool) => (
+          <div
+            key={tool.path}
+            className="link-card"
+            onClick={() => navigate(tool.path)}
+            style={{ cursor: 'pointer' }}
+          >
+            <div className="link-card__icon">{tool.icon}</div>
+            <div>
+              <div className="link-card__title">{tool.title}</div>
+              <div className="link-card__desc">{tool.desc}</div>
+            </div>
+          </div>
+        ))}
+      </div>
 
-      <h3 style={{ marginTop: '24px' }}>🌐 Externe Webseiten</h3>
+      <h3 style={{ marginTop: '24px' }}>Externe Webseiten</h3>
       {loadingWebsites ? (
         <p className="muted">Lade Links...</p>
       ) : websites.length === 0 ? (