feat: add multi-server support via GITEA_SERVERS env var

Allows connecting to multiple Gitea instances from a single MCP server.
Set GITEA_SERVERS as a JSON object mapping names to {host, token, insecure}
configs. Every tool gets an optional "server" parameter, and a new
"list_servers" tool is added to discover available connections.

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

cmd/cmd.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"os"
@@ -57,6 +58,7 @@ func init() {
 		fmt.Fprintf(w, "  GITEA_HOST\tOverride Gitea host URL\n")
 		fmt.Fprintf(w, "  GITEA_INSECURE\tSet to 'true' to ignore TLS errors\n")
 		fmt.Fprintf(w, "  GITEA_READONLY\tSet to 'true' for read-only mode\n")
+		fmt.Fprintf(w, "  GITEA_SERVERS\tJSON object mapping server names to {host, token, insecure} configs\n")
 		fmt.Fprintf(w, "  MCP_MODE\tOverride transport mode\n")
 		w.Flush()
 	}
@@ -91,6 +93,17 @@ func init() {
 	if os.Getenv("GITEA_INSECURE") == "true" {
 		flagPkg.Insecure = true
 	}
+
+	// Parse multi-server configuration from GITEA_SERVERS env var (JSON object).
+	// Example: {"dev":{"host":"https://gitea.dev.example.com","token":"xxx"},"prod":{...}}
+	if serversJSON := os.Getenv("GITEA_SERVERS"); serversJSON != "" {
+		var servers map[string]flagPkg.ServerConfig
+		if err := json.Unmarshal([]byte(serversJSON), &servers); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: failed to parse GITEA_SERVERS: %v\n", err)
+		} else {
+			flagPkg.Servers = servers
+		}
+	}
 }
 
 func Execute() {