chore: remove content script and update manifest for service worker

background.js

@@ -0,0 +1,10 @@
+chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {
+    if (changeInfo.status === "complete" && /^https?:/.test(tab.url)) {
+        chrome.scripting.executeScript({
+            target: { tabId },
+            files: ["main.js"]
+        }).catch(err => {
+            console.warn("Injection failed:", err);
+        });
+    }
+});