Replace Tailwind CSS CDN with Vite build-time compilation

Use Vite with @tailwindcss/vite to compile CSS at build time instead
of loading the ~100KB Tailwind browser runtime from CDN on every page.

- vite.config.js: Tailwind plugin, content-hashed CSS output + manifest
- dev/vite_hook.clj: shadow-cljs hook runs `vite build` automatically
- server.clj: reads Vite JSON manifest for hashed CSS filename
- build-ui.sh: runs `npx vite build` before shadow-cljs release

No workflow change — shadow-cljs watch/compile triggers Vite via hook.

Author: andriytyurnikov

.gitignore

@@ -30,10 +30,13 @@ scripts/code-format
 node_modules/
 public/
 
-# compiled frontend output
+# compiled frontend output (shadow-cljs)
 resource/public/main.js
 resource/public/main*.js
 resource/public/manifest.edn
+# compiled frontend output (vite)
+resource/public/main*.css
+resource/public/css-manifest.json
 
 # claude files
 CLAUDE.md

dev/vite_hook.clj

@@ -0,0 +1,60 @@
+(ns vite-hook
+  "Shadow-cljs build hook: runs Vite CSS build.
+   Dev mode: one-shot build + background watcher for live updates.
+   Release/compile: one-shot build only."
+  (:import [java.lang ProcessBuilder ProcessBuilder$Redirect]))
+
+(defonce ^:private state (atom {}))
+
+(defn- clean-old-css!
+  "Removes previously built CSS files and manifest from resource/public/."
+  []
+  (doseq [f (.listFiles (java.io.File. "resource/public"))]
+    (let [name (.getName f)]
+      (when (or (and (.startsWith name "main.") (.endsWith name ".css"))
+                (= name "css-manifest.json"))
+        (.delete f)))))
+
+(defn- run-vite-build!
+  "Runs `npx vite build` synchronously. Returns true on success.
+   In dev mode, logs warning on failure instead of crashing the REPL."
+  []
+  (clean-old-css!)
+  (let [proc (-> (ProcessBuilder. ["npx" "vite" "build" "--mode" "development"])
+                 (.redirectError ProcessBuilder$Redirect/INHERIT)
+                 (.redirectOutput ProcessBuilder$Redirect/INHERIT)
+                 (.start))
+        exit (.waitFor proc)]
+    (if (zero? exit)
+      true
+      (do (println "[vite] CSS build failed (exit" exit ") — fix your CSS and save again")
+          false))))
+
+(defn- start-watcher!
+  "Starts `vite build --watch` in the background for live CSS updates."
+  []
+  (when-let [^Process old (:process @state)]
+    (when (.isAlive old) (.destroyForcibly old)))
+  (let [proc (-> (ProcessBuilder. ["npx" "vite" "build" "--watch" "--mode" "development"])
+                 (.redirectError ProcessBuilder$Redirect/INHERIT)
+                 (.redirectOutput ProcessBuilder$Redirect/INHERIT)
+                 (.start))]
+    (swap! state assoc :process proc)
+    (when-not (:shutdown-hook? @state)
+      (.addShutdownHook (Runtime/getRuntime)
+        (Thread. #(when-let [^Process p (:process @state)]
+                    (when (.isAlive p) (.destroyForcibly p)))))
+      (swap! state assoc :shutdown-hook? true))))
+
+(defn build-css
+  "Shadow-cljs build hook. Compiles CSS via Vite at :configure stage.
+   In dev mode, also starts a background watcher for live updates."
+  {:shadow.build/stage :configure}
+  [build-state & _args]
+  (let [dev? (= :dev (:shadow.build/mode build-state))
+        ok?  (run-vite-build!)]
+    (when (and (not ok?) (not dev?))
+      (throw (ex-info "[vite] CSS build failed" {})))
+    (when dev?
+      (start-watcher!)))
+  build-state)