remove Tailwind + DaisyUI theme + heroicons plugin, admin fully custom CSS (Phase 7)

replace Tailwind CLI with esbuild for admin CSS bundling. admin now uses
hand-written utility classes (admin/utilities.css), static heroicon CSS
generated by mix generate_admin_icons, plain CSS colour themes extracted
from DaisyUI plugin config, and minimal resets. rename app.css to admin.css
for clarity alongside shop.css. delete vendor/daisyui-theme.js and
vendor/heroicons.js. no Tailwind dependency remains in the project.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/vendor/heroicons.js

@@ -1,43 +0,0 @@
-const plugin = require("tailwindcss/plugin")
-const fs = require("fs")
-const path = require("path")
-
-module.exports = plugin(function({matchComponents, theme}) {
-  let iconsDir = path.join(__dirname, "../../deps/heroicons/optimized")
-  let values = {}
-  let icons = [
-    ["", "/24/outline"],
-    ["-solid", "/24/solid"],
-    ["-mini", "/20/solid"],
-    ["-micro", "/16/solid"]
-  ]
-  icons.forEach(([suffix, dir]) => {
-    fs.readdirSync(path.join(iconsDir, dir)).forEach(file => {
-      let name = path.basename(file, ".svg") + suffix
-      values[name] = {name, fullPath: path.join(iconsDir, dir, file)}
-    })
-  })
-  matchComponents({
-    "hero": ({name, fullPath}) => {
-      let content = fs.readFileSync(fullPath).toString().replace(/\r?\n|\r/g, "")
-      content = encodeURIComponent(content)
-      let size = theme("spacing.6")
-      if (name.endsWith("-mini")) {
-        size = theme("spacing.5")
-      } else if (name.endsWith("-micro")) {
-        size = theme("spacing.4")
-      }
-      return {
-        [`--hero-${name}`]: `url('data:image/svg+xml;utf8,${content}')`,
-        "-webkit-mask": `var(--hero-${name})`,
-        "mask": `var(--hero-${name})`,
-        "mask-repeat": "no-repeat",
-        "background-color": "currentColor",
-        "vertical-align": "middle",
-        "display": "inline-block",
-        "width": size,
-        "height": size
-      }
-    }
-  }, {values})
-})