ci: switch versioning from CalVer to SemVer

Go module tooling requires v-prefixed semver tags (go install @latest
ignores CalVer tags entirely), GoReleaser errors on non-semver tags,
and zero-padded CalVer months are invalid semver. Old CalVer tags and
releases were deleted due to pre-release security issues; relaunch
tags as v1.0.0.

- Workflow tag triggers: [0-9]* -> v[0-9]* (Gitea + GitHub relay)
- cliff.toml tag_pattern: regex v[0-9].* (was matching everything --
  tag_pattern is regex since git-cliff 1.4, not glob)
- Docker image tags drop the v prefix per registry convention

.gitea/workflows/release-binaries.yml

@@ -3,7 +3,7 @@ name: Release Binaries
 on:
   push:
     tags:
-      - "[0-9]*"
+      - "v[0-9]*"
 
 jobs:
   release: