chore: add 'just run-release' (build web + run server with embed-web)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

justfile

@@ -4,6 +4,12 @@ set dotenv-load
 run:
     cargo run -p server
 
+# Build the web SPA + run the server in release mode with the SPA embedded (served at /)
+run-release:
+    # build.rs embeds web/dist, so the frontend must be built first
+    cd web && pnpm build
+    cargo run -p server --release --features embed-web
+
 # Seed the baseline Spectrum cataloguing vocabularies + field definitions (idempotent)
 seed:
     cargo run -p server -- seed