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>

backend/tools/hasher.py

@@ -0,0 +1,39 @@
+from flask import Blueprint, request, jsonify
+import hashlib
+import bcrypt
+from util.logger import logger
+from auth.token import verify_token
+
+hasher_blueprint = Blueprint('hasher_tool', __name__)
+
+
+@hasher_blueprint.route('/api/hash/sha256', methods=['POST'])
+def hash_sha256():
+    user = verify_token()
+    if not user:
+        return jsonify({"message": "Nicht autorisiert"}), 401
+    try:
+        data = request.get_json()
+        text = data.get("text", "")
+        result = hashlib.sha256(text.encode()).hexdigest()
+        logger.info(f"SHA256 erstellt von {user['username']}")
+        return jsonify({"sha256": result, "by": user['username']})
+    except Exception as e:
+        logger.error(f"Fehler SHA256: {e}")
+        return jsonify({"message": "Fehler beim Hashen"}), 500
+
+
+@hasher_blueprint.route('/api/hash/bcrypt', methods=['POST'])
+def hash_bcrypt():
+    user = verify_token()
+    if not user:
+        return jsonify({"message": "Nicht autorisiert"}), 401
+    try:
+        data = request.get_json()
+        text = data.get("text", "")
+        hashed = bcrypt.hashpw(text.encode(), bcrypt.gensalt()).decode()
+        logger.info(f"bcrypt erstellt von {user['username']}")
+        return jsonify({"bcrypt": hashed, "by": user['username']})
+    except Exception as e:
+        logger.error(f"Fehler bcrypt: {e}")
+        return jsonify({"message": "Fehler beim Hashen"}), 500