feat(签章验签): 完善OFD加密、签章与验签能力，统一国密实现，优化界面文案与交互

go.mod

@@ -3,11 +3,14 @@ module github.com/xiaoqidun/ofdgo
 go 1.26.0
 
 require (
+	github.com/emmansun/gmsm v0.44.1
+	github.com/go-fonts/latin-modern v0.3.3
 	github.com/go-text/typesetting v0.3.5
 	github.com/gogpu/gg v0.52.5
 	github.com/tdewolff/canvas v0.0.0-20260913163248-dd4999d1c76a
 	github.com/tdewolff/font v0.0.0-20260913163313-54f98bb59ee6
 	github.com/xiaoqidun/jbig2 v1.1.1
+	golang.org/x/crypto v0.57.0
 	golang.org/x/image v0.46.0
 	golang.org/x/text v0.42.0
 )
@@ -22,7 +25,6 @@ require (
 	github.com/andybalholm/brotli v1.2.2 // indirect
 	github.com/benoitkugler/textlayout v0.3.2 // indirect
 	github.com/benoitkugler/textprocessing v0.0.6 // indirect
-	github.com/go-fonts/latin-modern v0.3.3 // indirect
 	github.com/gogpu/gpucontext v0.28.0 // indirect
 	github.com/gogpu/gputypes v0.5.2 // indirect
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect