feat: support config ignore patterns

[cyberchen1995]

Summary

• add config.optional.ignore with .gitignore-compatible path patterns
• apply ignore rules before file scanning and archive traversal
• avoid duplicate version output for -version

Test Plan

• env GOCACHE=/private/tmp/opensca-go-build-cache GOTMPDIR=/private/tmp go test . ./cmd/config ./opensca ./opensca/walk ./opensca/sca/filter
• env GOCACHE=/private/tmp/opensca-go-build-cache GOTMPDIR=/private/tmp go run . -version
• git diff --check