add make-release.sh, svatantrya.asc, and update HANDOFF.md

- make-release.sh: automated release script (tests, lint, build, GPG sign, SHA-256, Gitea)
- svatantrya.asc: PGP public key for release verification
- HANDOFF.md: updated release workflow documentation
- willexecutors.py: input validation for addresses, fees, and API responses
- manifest.json: fixed version back to 0.6.1
- test_core_plugin_base.py: updated baltx_fees default

.gitignore

@@ -4,3 +4,4 @@
 bal-electrum-plugin.zip
 electrum-src/
 preview_*.png
+.env