chore: inject the version into main instead of a module path

The `-X` target carried the full module path in both the Makefile and
.goreleaser.yaml, so any change to the module path silently turned the
injection into a no-op and shipped a binary reporting "dev". Target
`main.version` instead, which no longer names the module, and fail
`make checks` when the injection stops taking effect.

Assisted-by: Codet:GPT-5.1-Codex

.goreleaser.yaml

@@ -65,7 +65,7 @@ builds:
   flags:
   - -trimpath
   ldflags:
-  - -s -w -X gitea.com/gitea/runner/internal/pkg/ver.version={{ .Summary }}
+  - -s -w -X main.version={{ .Summary }}
   binary: >-
     {{ .ProjectName }}-
     {{- .Version }}-