Add light/dark theme toggle, fix dark theme text contrast

Theme state persists via localStorage, applied pre-paint by theme-init.js
to avoid flash. All JS moved to external files (app.js, theme-init.js)
to keep script-src 'self' CSP intact, no inline scripts.

Dark theme footer/notice/tagline colors were too close to the background
(footer nearly matched the card border color) and hard to read; brightened
to readable grays while leaving the light theme and submit button untouched.

1 files changed, 5 insertions, 0 deletions

diff --git a/static/theme-init.js b/static/theme-init.js
new file mode 100644
index 0000000..95b9a95
--- /dev/null
+++ b/static/theme-init.js
@@ -0,0 +1,5 @@
+(function() {
+    if (localStorage.getItem('nymdrop-theme') === 'light') {
+        document.documentElement.setAttribute('data-theme', 'light');
+    }
+})();