Trigger Docker and packages workflows only for semantic tags

Go module versioning expect Git tags to start with the letter v.

The goal is to keep the existing naming convention for generated
artifacts and have proper versioning for the Go module.

.github/workflows/docker.yml

@@ -4,7 +4,7 @@ on:
     - cron: '0 1 * * *'
   push:
     tags:
-      - '*.*.*'
+      - '[0-9]+.[0-9]+.[0-9]+'
   pull_request:
     branches: [ main ]
 jobs:

.github/workflows/packages.yml

@@ -3,7 +3,7 @@ permissions: read-all
 on:
   push:
     tags:
-      - '*.*.*'
+      - '[0-9]+.[0-9]+.[0-9]+'
 jobs:
   debian-package-builder:
     name: Build Debian Packages