Remove the Go backend, JS frontend, Wails config and old build scripts; release.sh now wraps rust/release.sh

rust/.gitignore

@@ -1 +0,0 @@
-target/

rust/core/tests/fixtures/README.md

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+# Compatibility fixtures
+
+Generated by the last Go build of Alchementary Link with `cmd/genfixtures` (see commit f588a79,
+`git show f588a79:cmd/genfixtures/main.go`). Nexus Terminal must keep reading them unchanged:
+
+- `link.db` — a database through migration 006 with every protocol, a known host, a snippet,
+  IRC channel state and preferences.
+- `vault/vault.json` — a vault whose master password is `correct horse battery staple`.
+- `profiles.link` — an encrypted export with password `export-pass`.
+- `recordings/rec1.cast` — an asciicast v2 recording.
+
+Don't regenerate them; they are the reference for data written by the old app.