feat(actions)!: add RUN_RETENTION_DAYS to delete old action runs (#38855)

Gitea keeps completed Actions runs forever. Artifacts and logs expire on
their own schedule, but the run rows never go away, so `action_run` and
its child tables grow without bound.

Adds `RUN_RETENTION_DAYS` to delete completed runs along with their
jobs, tasks and anything the earlier expiries left behind. It defaults
to 400 days, matching how long GitHub keeps run history browsable. A
dedicated `cleanup_action_runs` cron task performs the cleanup, so
admins can schedule it separately from the nightly artifact and log
sweep.

`0` now means "keep forever" for all three retention settings, where
`LOG_RETENTION_DAYS` and `ARTIFACT_RETENTION_DAYS` previously took it
literally and deleted everything at the next sweep.

Docs: https://gitea.com/gitea/docs/pulls/502

----

## ⚠️ BREAKING ⚠️

`RUN_RETENTION_DAYS` defaults to 400, so completed runs older than that
are deleted when the cron task next runs at midnight. Set
`RUN_RETENTION_DAYS = 0` before upgrading to keep all runs.

---------

Co-authored-by: bircni <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

services/context/base_form.go

@@ -69,12 +69,20 @@ func (b *Base) FormBool(key string) bool {
 // FormOptionalBool returns an optional.Some(true) or optional.Some(false) if the value
 // for the provided key exists in the form else it returns optional.None[bool]()
 func (b *Base) FormOptionalBool(key string) optional.Option[bool] {
-	value := b.Req.FormValue(key)
-	if len(value) == 0 {
+	s := b.Req.FormValue(key)
+	if s == "" {
 		return optional.None[bool]()
 	}
-	s := b.Req.FormValue(key)
 	v, _ := strconv.ParseBool(s)
 	v = v || strings.EqualFold(s, "on")
 	return optional.Some(v)
 }
+
+func (b *Base) FormOptionalInt64(key string) optional.Option[int64] {
+	s := b.Req.FormValue(key)
+	v, err := strconv.ParseInt(s, 10, 64)
+	if s == "" || err != nil {
+		return optional.None[int64]()
+	}
+	return optional.Some(v)
+}