feat: Material Icons, customizable app name & dark/light mode toggle

- Add Google Material Icons integration with smart_toy robot icon
- Implement app_settings database table for persistent configuration
- Add App Name customization in Settings (changes navigation & title)
- Add Dark/Light Mode theme switcher
  - Dark Mode: Lightened black (#0f0f0f) with blue accents (#0a84ff)
  - Light Mode: Clean white/gray with red accents (#ef4444)
- Create context_processor for global app_settings injection
- Redesign Settings page with new App Design section
- Optimize CSS: 724 additions, reduced complexity
- Remove outdated agent reminders (70 lines cleanup)

app.py

@@ -289,6 +289,38 @@ def init_journal():
         )
     """)
     
+    # App-Settings Tabelle für globale Einstellungen
+    con.execute("""
+        CREATE TABLE IF NOT EXISTS app_settings (
+            key TEXT PRIMARY KEY,
+            value TEXT,
+            updated_at TEXT
+        )
+    """)
+    
+    # Default-Werte setzen falls nicht vorhanden
+    con.execute("""
+        INSERT OR IGNORE INTO app_settings (key, value, updated_at)
+        VALUES ('app_name', 'Frankenbot', ?), ('theme', 'dark', ?)
+    """, (datetime.now().isoformat(), datetime.now().isoformat()))
+    
+    con.commit()
+    con.close()
+
+def get_app_setting(key: str, default=None):
+    """Holt eine App-Einstellung aus der Datenbank."""
+    con = sqlite3.connect(EMAIL_JOURNAL_DB)
+    row = con.execute("SELECT value FROM app_settings WHERE key=?", (key,)).fetchone()
+    con.close()
+    return row[0] if row else default
+
+def set_app_setting(key: str, value: str):
+    """Setzt eine App-Einstellung in der Datenbank."""
+    con = sqlite3.connect(EMAIL_JOURNAL_DB)
+    con.execute("""
+        INSERT OR REPLACE INTO app_settings (key, value, updated_at)
+        VALUES (?, ?, ?)
+    """, (key, value, datetime.now().isoformat()))
     con.commit()
     con.close()
 
@@ -347,6 +379,14 @@ app = Flask(__name__)
 logging.basicConfig(level=logging.INFO)
 logger = logging.getLogger(__name__)
 
+@app.context_processor
+def inject_app_settings():
+    """Macht App-Settings in allen Templates verfügbar."""
+    return {
+        'app_name': get_app_setting('app_name', 'Frankenbot'),
+        'theme': get_app_setting('theme', 'dark')
+    }
+
 AGENT_KEYWORDS = {
     'researcher': ['recherche', 'recherchieren', 'suchen', 'informationen', 'trends', 'forschung', 'web'],
     'zusammenfasser': ['zusammenfassung', 'zusammenfassen', 'konsolidieren', 'übersicht'],
@@ -2752,8 +2792,21 @@ def email_log_view():
 
 @app.route('/settings', methods=['GET', 'POST'])
 def settings():
-    """Poller-Einstellungen zur Laufzeit ändern."""
+    """App-Einstellungen & Poller-Einstellungen zur Laufzeit ändern."""
     if request.method == 'POST':
+        # App-Name & Theme Einstellungen
+        if 'app_name' in request.form:
+            app_name = request.form.get('app_name', 'Frankenbot').strip()
+            theme = request.form.get('theme', 'dark')
+            if app_name:
+                set_app_setting('app_name', app_name)
+                set_app_setting('theme', theme)
+                flash(f'App-Einstellungen gespeichert: {app_name} ({theme} mode)', 'success')
+            else:
+                flash('App-Name darf nicht leer sein.', 'warning')
+            return redirect(url_for('settings'))
+        
+        # Poller-Einstellungen
         try:
             poll_interval = int(request.form.get('poll_interval', 120))
             failsafe_window = int(request.form.get('failsafe_window', 600))
@@ -2776,12 +2829,18 @@ def settings():
     ).fetchall()
     con.close()
     journal_stats = {row[0]: row[1] for row in journal_rows}
+    
+    # App-Einstellungen aus DB laden
+    app_name = get_app_setting('app_name', 'Frankenbot')
+    theme = get_app_setting('theme', 'dark')
 
     return render_template('settings.html',
                            agents=AGENTS,
                            poller_settings=poller_settings,
                            journal_stats=journal_stats,
-                           telegram_config=TELEGRAM_CONFIG)
+                           telegram_config=TELEGRAM_CONFIG,
+                           app_name=app_name,
+                           theme=theme)
 
 
 @app.route('/settings/journal-clear', methods=['POST'])