feat: Implement virtual hosting for multi-domain Gemini server

- Add hostname-based request routing for multiple capsules per server
- Parse virtual host configs from TOML sections ([hostname])
- Implement per-host certificate and content isolation
- Add comprehensive virtual host testing and validation
- Update docs and examples for multi-host deployments

This enables Pollux to serve multiple Gemini domains from one instance,
providing the foundation for multi-tenant Gemini hosting.

examples/development.toml

@@ -0,0 +1,30 @@
+# Pollux Development Configuration
+#
+# Example configuration for local development with self-signed certificates.
+# NOT suitable for production use.
+
+bind_host = "127.0.0.1"
+port = 1965
+log_level = "debug"
+max_concurrent_requests = 100
+
+# Local development site
+["localhost"]
+root = "./content"
+cert = "./tmp/cert.pem"
+key = "./tmp/key.pem"
+
+# Alternative hostname for testing
+["gemini.local"]
+root = "./content"
+cert = "./tmp/cert.pem"
+key = "./tmp/key.pem"
+
+# Generate self-signed certificates with:
+# mkdir -p tmp
+# openssl req -x509 -newkey rsa:2048 \
+#   -keyout tmp/key.pem \
+#   -out tmp/cert.pem \
+#   -days 365 \
+#   -nodes \
+#   -subj "/CN=localhost"