Fix static asset 404s and build-time SITE_NAME

Two runtime gaps found via hwatu after the first successful deploy:
- /pkg/*.{js,wasm,css} 404'd because the running binary looked for
  target/site (Cargo.toml's site-root, a build-time path) but the
  deploy step copies the bundle to releases/<sha>/site with no
  target/ prefix - LEPTOS_SITE_ROOT=site in the runtime env corrects
  it.
- SITE_NAME is read via option_env! (compile-time), so writing it
  only into the runtime env file never reached the binary - the
  wordmark stayed "portal". Now exported for the Build step too.

Verified live: applied both fixes directly to the running deployment
first (no CI round-trip), confirmed via hwatu (no console errors,
hero renders, all three alternatives' forms present) before folding
them back into the workflow.

.gitea/workflows/deploy.yml

@@ -41,8 +41,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      # SITE_NAME is read via option_env! (src/app.rs) - compile-time,
+      # not a runtime env var - so it has to be set here, not just in
+      # the "Write service env" step below.
       - name: Build
-        run: cargo leptos build --release
+        run: SITE_NAME=${{ vars.PORTAL_SITE_NAME }} cargo leptos build --release
 
       - name: Ship release
         run: |
@@ -72,6 +75,11 @@ jobs:
           CONTENT_BRANCH=main
           SITE_NAME=${{ vars.PORTAL_SITE_NAME }}
           LEPTOS_SITE_ADDR=0.0.0.0:3010
+          # Cargo.toml's site-root ("target/site") is a build-time path;
+          # the deploy layout copies the bundle to releases/<sha>/site
+          # (no target/ prefix) - override so the running binary looks
+          # in the right place for /pkg/*.
+          LEPTOS_SITE_ROOT=site
           EOF
 
       # No sudo: the runner's own unit sets NoNewPrivileges=yes, which