fix: make debug mode toggle work at runtime

The debug/insecure warning banner was only controlled by the compile-time
DEBUG constant. The settings easter egg checkbox toggled state.debugMode
and the runtime log flag, but neither index.js nor helpers.js checked
these runtime values — the banner was created/updated based solely on
the compile-time constant.

Changes:
- Extract banner logic into updateDebugBanner() in helpers.js that
  checks isDebug() (combines compile-time DEBUG and runtime debugMode)
- Banner is dynamically created/removed: appears when debug is enabled,
  removed when disabled (no stale banners)
- index.js init() syncs runtime debug flag from persisted state before
  first render, then delegates to updateDebugBanner()
- settings.js calls updateDebugBanner() after the checkbox change so
  the banner immediately reflects the new state
- Debug mode persists across popup close/reopen via state.debugMode

Fixes the bug where the settings debug toggle had no visible effect.

src/popup/index.js

@@ -1,18 +1,19 @@
 // AutistMask popup entry point.
 // Loads state, initializes views, triggers first render.
 
-const { DEBUG } = require("../shared/constants");
 const {
     state,
     saveState,
     loadState,
     currentNetwork,
 } = require("../shared/state");
+const { isDebug, setRuntimeDebug } = require("../shared/log");
 const { refreshPrices } = require("../shared/prices");
 const { refreshBalances } = require("../shared/balances");
 const {
     $,
     showView,
+    updateDebugBanner,
     setRenderMain,
     pushCurrentView,
     goBack,
@@ -209,21 +210,11 @@ async function init() {
     await loadState();
     applyTheme(state.theme);
 
-    const net = currentNetwork();
-    if (DEBUG || net.isTestnet) {
-        const banner = document.createElement("div");
-        banner.id = "debug-banner";
-        if (DEBUG && net.isTestnet) {
-            banner.textContent = "DEBUG / INSECURE [TESTNET]";
-        } else if (net.isTestnet) {
-            banner.textContent = "[TESTNET]";
-        } else {
-            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;";
-        document.body.prepend(banner);
-    }
+    // Sync runtime debug flag from persisted state before first render
+    setRuntimeDebug(state.debugMode);
+
+    // Create the debug/testnet banner if needed (uses runtime debug state)
+    updateDebugBanner();
 
     // Auto-default active address
     if (