chore: migrate CI to Gitea actions and update module path

docs/library-usage.md

@@ -5,7 +5,7 @@
 ## Installation
 
 ```bash
-go get codeberg.org/petrbalvin/nuntius/pkg/contactform
+go get sourcedock.dev/petrbalvin/nuntius/pkg/contactform
 ```
 
 Because nuntius ships with no `go.sum` entries from third-party modules, this import pulls in only stdlib transitively.
@@ -118,7 +118,7 @@ import (
     "fmt"
     "os"
 
-    "codeberg.org/petrbalvin/nuntius/pkg/contactform"
+    "sourcedock.dev/petrbalvin/nuntius/pkg/contactform"
 )
 
 func main() {
@@ -175,7 +175,7 @@ import (
     "log"
     "net/http"
 
-    "codeberg.org/petrbalvin/nuntius/pkg/contactform"
+    "sourcedock.dev/petrbalvin/nuntius/pkg/contactform"
 )
 
 func contactHandler(w http.ResponseWriter, r *http.Request) {