ui: rename "Trim clip" dialog to "Trim VOD" / "VOD zuschneiden"

The dialog cuts a custom time-range out of a VOD; calling its result a
"clip" was overloaded with the separate Twitch Clips feature (which
this project handles in the dedicated Clips tab). Renaming the modal
title disambiguates without touching the per-VOD-card "Clip" button
(still the right verb for the action that opens it).

- EN: "Trim VOD"
- DE: "VOD zuschneiden"
- index.html static fallback updated to match the DE locale

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.html

@@ -48,7 +48,7 @@
     <div class="modal-overlay" id="clipModal">
         <div class="modal" style="background: #2b2b2b; max-width: 500px;">
             <button class="modal-close" onclick="closeClipDialog()">x</button>
-            <h2 style="color: #E5A00D; text-align: center; margin-bottom: 20px;" id="clipDialogTitle">Clip zuschneiden</h2>
+            <h2 style="color: #E5A00D; text-align: center; margin-bottom: 20px;" id="clipDialogTitle">VOD zuschneiden</h2>
 
             <!-- Start Zeit mit Slider -->
             <div style="margin-bottom: 15px;">