fix(web): header search dropdown no longer covers the sidebar

Anchor #header-search-overlay to the search bar (position:absolute inside a
relative .header-search-wrap) instead of position:fixed full-viewport width,
so the results drop down at the bar's width and the left sidebar stays visible.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

index.html

@@ -107,6 +107,10 @@
             <svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="11" cy="11" r="8"/><path d="m21 21-4.35-4.35"/></svg>
             <input id="header-search-input" type="text" placeholder="Suchen…" oninput="onHeaderSearch(this.value)" autocomplete="off">
             <button id="header-search-clear" onclick="closeHeaderSearch()" style="display:none;background:none;border:none;color:var(--text3);cursor:pointer;font-size:15px;padding:0;line-height:1;flex-shrink:0">✕</button>
+            <!-- Results drop down anchored to the search bar's width (not full-viewport), so the sidebar stays visible -->
+            <div id="header-search-overlay" style="display:none">
+              <div id="header-search-results"></div>
+            </div>
           </div>
           <div style="display:flex;align-items:center;gap:2px;flex-shrink:0">
             <button class="hbtn notif-bell-btn" onclick="toggleNotifPanel()" title="Benachrichtigungen" style="padding:8px;color:var(--text2)">
@@ -118,9 +122,6 @@
             </button>
           </div>
         </div>
-        <div id="header-search-overlay" style="display:none">
-          <div id="header-search-results"></div>
-        </div>
       </div>
 
       <!-- HOME -->