Global title bar on all screens, screen name in DEBUG banner

Move "AutistMask by @sneak" to a global title bar that appears
on every screen. Per-view headings demoted to h2 sub-headings.
Settings button moved to bottom of main view alongside Add
wallet. In DEBUG mode, the red banner now shows the current
screen name in parentheses (e.g. "DEBUG / INSECURE (main)").

src/popup/index.js

@@ -37,6 +37,12 @@ function showView(name) {
             el.classList.toggle("hidden", v !== name);
         }
     }
+    if (DEBUG) {
+        const banner = document.getElementById("debug-banner");
+        if (banner) {
+            banner.textContent = "DEBUG / INSECURE (" + name + ")";
+        }
+    }
 }
 
 // Browser-agnostic storage API
@@ -373,6 +379,7 @@ function backFromWalletAdd() {
 async function init() {
     if (DEBUG) {
         const banner = document.createElement("div");
+        banner.id = "debug-banner";
         banner.textContent = "DEBUG / INSECURE";
         banner.style.cssText =
             "background:#c00;color:#fff;text-align:center;font-size:10px;padding:1px 0;font-family:monospace;position:sticky;top:0;z-index:9999;";