Switch static server from nginx to static-web-server

Replace nginx:alpine-slim with the scratch-based static-web-server
image, reducing the final image size ~32MB -> ~23MB (28% smaller).

- Dockerfile: serve from static-web-server:2, copy site to /public
- sws.toml: mirror previous nginx behavior (compression, cache-control,
  SPA index fallback) plus security headers and /health endpoint
- Remove now-unused nginx.conf

sws.toml

@@ -0,0 +1,43 @@
+[general]
+
+#### Server
+
+# Listen on all interfaces, port 80 (matches previous nginx setup)
+host = "0.0.0.0"
+port = 80
+
+# Root directory of the static site (Hugo `public/` output)
+root = "/public"
+
+# Number of worker threads (0 = auto-detect based on CPU cores)
+threads-multiplier = 1
+
+# Log level
+log-level = "info"
+
+#### Performance / caching
+
+# On-the-fly gzip, brotli and zstd compression (replaces nginx `gzip on`)
+compression = true
+
+# Serve pre-compressed .gz/.br/.zst files from disk when present
+compression-static = true
+
+# Emit Cache-Control + ETag headers with sensible per-content-type defaults.
+# SWS applies long-lived caching to static assets (images, css, js, fonts)
+# and short/no-cache to HTML, replacing the manual nginx `expires 1y` blocks.
+cache-control-headers = true
+
+#### Routing
+
+# SPA-style fallback: serve index.html when a path is not found on disk,
+# mirroring the previous nginx `try_files $uri $uri/ /index.html`.
+page-fallback = "/public/index.html"
+
+#### Security
+
+# Opinionated security headers (safe defaults for a static site)
+security-headers = true
+
+# Health endpoint at /health for container/K8s liveness probes
+health = true