fix(L4): generate EIP-6963 provider UUID at install time

UUID is generated once via crypto.randomUUID(), persisted in
chrome.storage.local, and sent from the content script to the
inpage script via postMessage.

src/content/index.js

@@ -13,6 +13,23 @@ if (typeof browser !== "undefined") {
     (document.head || document.documentElement).appendChild(script);
 }
 
+// Send the persisted EIP-6963 provider UUID to the inpage script.
+// Generated once at install time and stored in chrome.storage.local.
+(function sendProviderUuid() {
+    const storage =
+        typeof browser !== "undefined"
+            ? browser.storage.local
+            : chrome.storage.local;
+    storage.get("eip6963Uuid", (items) => {
+        let uuid = items?.eip6963Uuid;
+        if (!uuid) {
+            uuid = crypto.randomUUID();
+            storage.set({ eip6963Uuid: uuid });
+        }
+        window.postMessage({ type: "AUTISTMASK_PROVIDER_UUID", uuid }, "*");
+    });
+})();
+
 // Relay requests from the page to the background script
 window.addEventListener("message", (event) => {
     if (event.source !== window) return;