Update dependencies and documentation

- Bumped p256k1.mleku.dev version from v1.0.1 to v1.0.3 in go.mod and updated go.sum accordingly.
- Updated deployment script to use Go version 1.25.3 and adjusted CGO settings for building the binary.
- Added new lines to POLICY_USAGE_GUIDE.md and RELAY_TESTING_GUIDE.md for improved documentation clarity.

go.mod

@@ -22,16 +22,12 @@ require (
 	honnef.co/go/tools v0.6.1
 	lol.mleku.dev v1.0.5
 	lukechampine.com/frand v1.5.1
-	p256k1.mleku.dev v1.0.1
+	p256k1.mleku.dev v1.0.3
 )
 
 require (
 	github.com/BurntSushi/toml v1.5.0 // indirect
-	github.com/btcsuite/btcd/btcec/v2 v2.3.6 // indirect
-	github.com/btcsuite/btcd/chaincfg/chainhash v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
-	github.com/decred/dcrd/crypto/blake256 v1.0.0 // indirect
-	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
 	github.com/dgraph-io/ristretto/v2 v2.3.0 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/felixge/fgprof v0.9.5 // indirect