feat: add About well to settings with build info and debug easter egg (#145)

## Summary

Add a new well at the bottom of the settings view displaying application info (license, author, version, build date, git commit hash linked to Gitea), and an easter egg that reveals a debug mode toggle after clicking the version number 10 times.

## Changes

- **`src/popup/index.html`**: Added About well with license, author, version, build date, and linked commit hash. Added hidden debug well with debug mode toggle.
- **`src/popup/views/settings.js`**: Populate About well from build-time constants. Implement version click counter (10 clicks reveals debug well). Wire up debug mode toggle to state and runtime logger.
- **`src/shared/buildInfo.js`** (new): Module exporting build-time constants (`BUILD_VERSION`, `BUILD_LICENSE`, `BUILD_AUTHOR`, `BUILD_COMMIT`, `BUILD_DATE`, `GITEA_COMMIT_URL`) injected by esbuild define.
- **`build.js`**: Read git commit hash (short + full) and version from package.json, pass as esbuild `define` constants. Also reads `GIT_COMMIT_SHORT`/`GIT_COMMIT_FULL` env vars for Docker builds.
- **`Dockerfile`**: Accept `GIT_COMMIT_SHORT` and `GIT_COMMIT_FULL` build args, set as env vars for the build step.
- **`Makefile`**: Pass git commit hashes as Docker build args.
- **`src/shared/state.js`**: Add `debugMode` boolean to state (persisted).
- **`src/shared/log.js`**: Add runtime debug flag that supplements the compile-time `DEBUG` constant. Debug mode toggle updates this flag immediately.

closes #144

Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: clawbot <clawbot@sneak.cloud>
Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: clawbot <clawbot@eeqj.de>
Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #145
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

src/popup/views/helpers.js

@@ -1,6 +1,6 @@
 // Shared DOM helpers used by all views.
 
-const { DEBUG } = require("../../shared/constants");
+const { isDebug } = require("../../shared/log");
 const {
     formatUsd,
     getPrice,
@@ -59,19 +59,37 @@ function showView(name) {
     clearFlash();
     state.currentView = name;
     saveState();
+    updateDebugBanner(name);
+}
+
+// Create or update the debug/insecure warning banner.
+// Called on every view switch and after the settings debug toggle changes.
+// The banner is shown when the compile-time DEBUG constant is true OR when
+// the user has enabled runtime debug mode via the settings easter egg, OR
+// when the active network is a testnet.
+function updateDebugBanner(viewName) {
+    const debug = isDebug();
     const net = currentNetwork();
-    if (DEBUG || net.isTestnet) {
-        const banner = document.getElementById("debug-banner");
-        if (banner) {
-            if (DEBUG && net.isTestnet) {
-                banner.textContent =
-                    "DEBUG / INSECURE [TESTNET] (" + name + ")";
-            } else if (net.isTestnet) {
-                banner.textContent = "[TESTNET]";
-            } else {
-                banner.textContent = "DEBUG / INSECURE (" + name + ")";
-            }
+    const show = debug || net.isTestnet;
+    let banner = document.getElementById("debug-banner");
+    if (show) {
+        if (!banner) {
+            banner = document.createElement("div");
+            banner.id = "debug-banner";
+            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);
         }
+        const suffix = viewName ? " (" + viewName + ")" : "";
+        if (debug && net.isTestnet) {
+            banner.textContent = "DEBUG / INSECURE [TESTNET]" + suffix;
+        } else if (net.isTestnet) {
+            banner.textContent = "[TESTNET]" + suffix;
+        } else {
+            banner.textContent = "DEBUG / INSECURE" + suffix;
+        }
+    } else if (banner) {
+        banner.remove();
     }
 }
 
@@ -417,6 +435,7 @@ module.exports = {
     showError,
     hideError,
     showView,
+    updateDebugBanner,
     setRenderMain,
     pushCurrentView,
     goBack,