refactor: remove SSE transport support from code and documentation (#97)

- Remove support and documentation for sse mode across all language README files
- Update CLI flags and help text to exclude references to sse mode
- Remove SSE server initialization in operation logic
- Adjust error messages to only mention stdio and http transport types
- Update logging setup to remove sse mode conditional logging

See the latest documentation: https://modelcontextprotocol.io/specification/2025-06-18/basic/transports

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/97
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

pkg/log/log.go

@@ -48,7 +48,7 @@ func Default() *zap.Logger {
 			MaxAge:     30,
 		}))
 
-		if flag.Mode == "http" || flag.Mode == "sse" {
+		if flag.Mode == "http" {
 			wss = append(wss, zapcore.AddSync(os.Stdout))
 		}