[log] Add debug logging to server HTTP server scaffold (#5388)

## Summary

Adds `logHTTPServer` debug logger to `internal/server/http_server.go` to
improve visibility into HTTP server creation and configuration during
startup.

## Changes

Added 4 meaningful debug log calls:
- `newHTTPServer`: logs the address when creating the HTTP server
- `buildMCPHTTPServer`: logs build parameters (address, auth/HMAC
enabled state), resolved session timeout, and completion status

## Why This Helps

The `buildMCPHTTPServer` function is the central scaffold used by both
routed and unified modes. With `DEBUG=server:*`, operators can now
trace:
- Which address the server binds to
- Whether auth and HMAC signing are active
- What session timeout was resolved from the environment

## Validation

- `go test ./internal/...` passes (exit 0)
- Logger follows `pkg:filename` naming convention:
`"server:http_server"`
- No side effects in log arguments (only reads existing variables)
- Single file modified




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Author: lpcox

internal/server/http_server.go

@@ -5,9 +5,13 @@ import (
 	"time"
 
 	"github.com/github/gh-aw-mcpg/internal/config"
+	"github.com/github/gh-aw-mcpg/internal/logger"
 )
 
+var logHTTPServer = logger.New("server:http_server")
+
 func newHTTPServer(addr string, handler http.Handler) *http.Server {
+	logHTTPServer.Printf("Creating HTTP server: addr=%s", addr)
 	return &http.Server{
 		Addr:    addr,
 		Handler: handler,
@@ -24,9 +28,12 @@ func buildMCPHTTPServer(
 	apiKey, hmacSecret string,
 	routeBuilder func(mux *http.ServeMux, sessionTimeout time.Duration),
 ) *http.Server {
+	logHTTPServer.Printf("Building MCP HTTP server: addr=%s, auth_enabled=%v, hmac_enabled=%v", addr, apiKey != "", hmacSecret != "")
 	mux := http.NewServeMux()
 	registerCommonEndpoints(mux, unifiedServer, apiKey)
 	sessionTimeout := config.GetGatewaySessionTimeoutFromEnv()
+	logHTTPServer.Printf("Session timeout configured: %s", sessionTimeout)
 	routeBuilder(mux, sessionTimeout)
+	logHTTPServer.Printf("MCP HTTP server scaffold ready: addr=%s", addr)
 	return newHTTPServer(addr, mux)
 }