First Commit, Code by Claude 4.7 Opus

content.js

@@ -0,0 +1,47 @@
+let gainNode = null;
+let audioCtx  = null;
+let sourceMap = new WeakMap();
+
+function setVolume(percent) {
+    const factor = percent / 100;
+    document.querySelectorAll('video, audio').forEach(el => {
+        if (!sourceMap.has(el)) {
+            if (!audioCtx) {
+                audioCtx = new AudioContext();
+            }
+            try {
+                const src  = audioCtx.createMediaElementSource(el);
+                const gain = audioCtx.createGain();
+                src.connect(gain);
+                gain.connect(audioCtx.destination);
+                sourceMap.set(el, gain);
+            } catch (e) {
+                // Element bereits in einem anderen Context
+                return;
+            }
+        }
+        sourceMap.get(el).gain.value = factor;
+    });
+}
+
+// Beim Laden: gespeicherten Wert anwenden
+chrome.storage.local.get('volume', ({ volume }) => {
+    if (volume !== undefined) setVolume(volume);
+});
+
+// Auf Nachrichten vom Popup hören
+chrome.runtime.onMessage.addListener(({ volume }) => {
+    if (volume !== undefined) setVolume(volume);
+});
+
+// Neue Media-Elemente automatisch erfassen
+const observer = new MutationObserver(() => {
+    chrome.storage.local.get('volume', ({ volume }) => {
+        if (volume !== undefined && volume !== 100) {
+            setVolume(volume);
+        }
+    });
+});
+observer.observe(document.body, {
+    childList: true, subtree: true
+});