Add dev-watch recipe with chokidar-cli for live rebuild on CSS/JS changes

- just dev now spawns a background chokidar watcher alongside the PHP server
- CSS/JS changes auto-rebuild into dist/ (~200ms per rebuild)
- just stop kills both the PHP server and the watcher
- just dev-watch still available standalone for split-terminal workflows
- chokidar-cli added as devDependency

justfile

@@ -11,10 +11,30 @@ default:
 setup:
     @bash scripts/setup-dev.sh
 
+# One-shot build of all frontend assets (run before `dev` if sources changed)
 [group('dev')]
-dev: migrate
+dev-build:
+    @node scripts/build.mjs
+
+# Watch CSS/JS sources and rebuild on change.
+# Run in a separate terminal alongside `just dev`.
+[group('dev')]
+dev-watch:
+    @npx chokidar \
+        "app/public/assets/css/**/*.css" \
+        "app/public/assets/js/app/**/*.js" \
+        --initial \
+        -c "node scripts/build.mjs"
+
+[group('dev')]
+dev: dev-build migrate
     @xdg-open http://127.0.0.1:8000 &
     @xdg-open http://127.0.0.1:8000/admin/ &
+    @npx chokidar \
+        "app/public/assets/css/**/*.css" \
+        "app/public/assets/js/app/**/*.js" \
+        -c "node scripts/build.mjs" &
+    @sleep 0.5
     @php \
         -d upload_max_filesize=8192M \
         -d post_max_size=8704M \
@@ -26,7 +46,9 @@ dev: migrate
 
 [group('dev')]
 stop:
-    @pkill -f "php -S 127.0.0.1:8000" 2>/dev/null && echo "stopped" || echo "no server running"
+    @pkill -f "php -S 127.0.0.1:8000" 2>/dev/null; \
+     pkill -f "chokidar.*assets/(css|js)" 2>/dev/null; \
+     echo "stopped"
 
 [group('dev')]
 logs: