Support plain HTTP mode for mc-proxy L7 deployment

Custom config package with optional TLS fields. When tls_cert/tls_key
are empty, serves plain HTTP (behind mc-proxy which terminates TLS).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

go.mod

@@ -6,6 +6,7 @@ require (
 	git.wntrmute.dev/mc/mcdsl v1.2.0
 	github.com/alecthomas/chroma/v2 v2.18.0
 	github.com/go-chi/chi/v5 v5.2.5
+	github.com/pelletier/go-toml/v2 v2.3.0
 	github.com/spf13/cobra v1.10.2
 	github.com/yuin/goldmark v1.7.12
 	github.com/yuin/goldmark-highlighting/v2 v2.0.0-20230729083705-37449abec8cc
@@ -20,7 +21,6 @@ require (
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
-	github.com/pelletier/go-toml/v2 v2.3.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	golang.org/x/net v0.48.0 // indirect