feat: bootstrap Go project layout (forgejo-mcp-broker-n84)

- Initialize go.mod with module path kode.naiv.no/olemd/forgejo-mcp-broker
- Create directory layout: cmd/broker + internal/{buildinfo,config,log,store,httpserver}
- Add Makefile with build/test/lint/tidy/clean targets and ldflags-injected build info
- Stub cmd/broker/main.go with --version support; real wiring follows in -t37
- Stub doc.go for each internal/* package, pointing to the issue that fills it in

Closes forgejo-mcp-broker-n84.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/broker/main.go

@@ -0,0 +1,31 @@
+// Command fjmcp-broker is an OAuth 2.1 authorization server and MCP session
+// broker that fronts forgejo-mcp. See ../../README.md and ../../docs/ for the
+// design.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"kode.naiv.no/olemd/forgejo-mcp-broker/internal/buildinfo"
+)
+
+func main() {
+	var showVersion bool
+	flag.BoolVar(&showVersion, "version", false, "print build info and exit")
+	flag.Parse()
+
+	if showVersion {
+		fmt.Printf("fjmcp-broker %s (rev %s, built %s)\n",
+			buildinfo.Version, buildinfo.GitRevision, buildinfo.BuildDate)
+		return
+	}
+
+	// Full startup wiring (config → log → store → httpserver) lands in
+	// forgejo-mcp-broker-t37. Until then this binary only serves --version
+	// so the bootstrap acceptance criteria can be exercised.
+	fmt.Fprintln(os.Stderr, "fjmcp-broker: runtime wiring not yet implemented (phase 1 in progress)")
+	fmt.Fprintln(os.Stderr, "Use --version to print build info.")
+	os.Exit(2)
+}