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

bal/manifest.json

@@ -5,6 +5,8 @@
     "description": "Provides free and decentralized Bitcoin inheritance support. Build time-locked 'will' transactions that transfer funds to your heirs if you stop refreshing them (dead-man's switch), optionally relayed by will-executor servers.",
     "author": "Svatantrya",
     "licence": "MIT",
-    "available_for": ["qt"],
+    "available_for": [
+        "qt"
+    ],
     "icon": "icons/bal32x32.png"
-}
+}