feat(ui): redesign UI with Tailwind CSS, CodeMirror 6, and new layout

- Replace all hand-written CSS with Tailwind utility classes
- Upgrade CodeMirror 5 to CodeMirror 6 (scoped @codemirror/* packages)
- Redesign layout with responsive sidebar navigation using JSX/Mithril
- Flatten admin routes (e.g. /admin/presets -> /presets)
- Add "remember me" login option with 2-week persistent cookie
- Add delete confirmation dialogs across admin pages
- Upgrade esbuild from 0.21 to 0.27 and update browser targets
- Add Inter and Roboto Mono variable fonts with subset script

build/generate-fonts.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+cd "$(dirname "$0")"
+
+declare -A FONTS=(
+  [InterVariable]=https://rsms.me/inter/font-files/InterVariable.woff2
+  [InterVariable-Italic]=https://rsms.me/inter/font-files/InterVariable-Italic.woff2
+  [RobotoMono]=https://raw.githubusercontent.com/googlefonts/RobotoMono/main/fonts/variable/RobotoMono%5Bwght%5D.ttf
+)
+
+for name in "${!FONTS[@]}"
+do
+  url="${FONTS[$name]}"
+  echo "Downloading $url"
+  TMP=$(mktemp)
+  curl "$url" -s --output "$TMP"
+  pyftsubset "$TMP" --output-file="../ui/css/$name.woff2" --flavor=woff2 --unicodes="U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+2000-206F,U+2074,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD" --layout-features+="tnum"
+done