cleanup: .settings-card.centered + .info-text + .stats-summary-grid

Three more inline-styled blocks moved into CSS classes:

- The Clips Info card had max-width:600px; margin:20px auto inline on the settings-card itself, plus color/line-height/white-space:pre-line inline on the info paragraph. Now .settings-card.centered (modifier for narrow-centred cards) and .info-text (multi-line description text with preserved authored line breaks).

- The Stats Summary KPI grid carried a 3-property grid declaration inline (display:grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap:12px). The layout is unique to this one container, but lifting it to .stats-summary-grid makes the markup self-documenting and matches the rest of the .stats-* class family.

Net: 3 inline style attributes gone, 3 new CSS rules.

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

src/index.html

@@ -304,9 +304,9 @@
                         <div class="clip-status" id="clipStatus"></div>
                     </div>
 
-                    <div class="settings-card" style="max-width: 600px; margin: 20px auto;">
+                    <div class="settings-card centered">
                         <h3 id="clipsInfoTitle">Info</h3>
-                        <p style="color: var(--text-secondary); line-height: 1.6; white-space: pre-line;" id="clipsInfoText">
+                        <p id="clipsInfoText" class="info-text">
                             Unterstutzte Formate:
                             - https://clips.twitch.tv/ClipName
                             - https://www.twitch.tv/streamer/clip/ClipName
@@ -431,7 +431,7 @@
 
                     <div class="settings-card">
                         <h3 id="statsSummaryTitle">Uebersicht</h3>
-                        <div id="statsSummaryGrid" style="display:grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap:12px;"></div>
+                        <div id="statsSummaryGrid" class="stats-summary-grid"></div>
                     </div>
 
                     <div class="settings-card">