refactor: Inline-Styles durch CSS-Klassen ersetzt

- 40+ Utility-Klassen in form.css (clickable, text-danger, flex-row, loading-state, etc.)
- share-menu position/z-index in chat.css statt inline
- index.html: 0 Inline-Styles (hidden-Attribut, CSS-Klassen)
- 12 JS-Dateien bereinigt: style.cssText/style.* durch classList ersetzt
- Bugfix: var(--danger) → var(--dangerous) (nicht existierende Variable)
- display:none Toggles → hidden-Attribut wo passend
- Hardcoded font-sizes in chat.css → var(--font-size)

15 Dateien, nur Frontend (CSS/JS/HTML), kein Backend

wwwroot/index.html

@@ -473,7 +473,7 @@
             </div>
           </div>
         </section>
-        <section id="settingsBackupSection" class="settings-section" style="display:none">
+        <section id="settingsBackupSection" class="settings-section" hidden>
           <h2>Daten</h2>
           <div class="setting-row">
             <div class="setting-info">
@@ -573,7 +573,7 @@
       <div class="form">
         <div class="section-header">
           <h2>API-Key</h2>
-          <button id="apiKeysCheckAllBtn" class="section-add-btn" style="margin-right: var(--badge-spacing); margin-left: auto;"><i class="fa fa-refresh"></i> Alle prüfen</button>
+          <button id="apiKeysCheckAllBtn" class="section-add-btn mr-badge ml-auto"><i class="fa fa-refresh"></i> Alle prüfen</button>
           <button id="apiKeysNewBtn" class="section-add-btn"><i class="fa fa-plus"></i> Neuer Key</button>
         </div>
         <div id="apiKeysList" class="admin-user-list"></div>
@@ -596,19 +596,19 @@
         </div>
       </div>
 
-      <div id="eventScannerStatus" style="display:none;padding:1em 2em;"></div>
+      <div id="eventScannerStatus" class="event-scanner-status" hidden></div>
 
       <div class="form">
         <div class="section-header">
           <h2>Key Scanner</h2>
-          <div style="display:flex;gap:.5rem;align-items:center">
+          <div class="flex-row">
             <button id="recheckAllScannedBtn" class="section-add-btn"><i class="fa fa-refresh"></i> Alle prüfen</button>
             <button id="scanQuickBtn" class="section-add-btn"><i class="fa fa-bolt"></i> Quick</button>
             <button id="scanWebBtn" class="section-add-btn"><i class="fa fa-globe"></i> Web</button>
             <button id="scanFullBtn" class="section-add-btn"><i class="fa fa-search"></i> Full</button>
           </div>
         </div>
-        <div id="scanStatus" style="font-size:.85em;color:var(--text-secondary);padding:0 0 .5rem 0"></div>
+        <div id="scanStatus" class="scan-status"></div>
         <div id="scannedKeysList" class="admin-user-list"></div>
         <div class="form-actions">
           <button hidden>&nbsp;</button>