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>

custom/conf/app.example.ini

@@ -2288,6 +2288,18 @@ LEVEL = Info
 ;RUN_AT_START = true
 ;SCHEDULE = @midnight
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Delete action runs older than RUN_RETENTION_DAYS
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;[cron.cleanup_action_runs]
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Deletes nothing while RUN_RETENTION_DAYS is 0
+;ENABLED = true
+;RUN_AT_START = false
+;SCHEDULE = @midnight
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Clean-up deleted branches
@@ -3008,16 +3020,20 @@ LEVEL = Info
 ;;
 ;; Default platform to get action plugins, `github` for `https://github.com`, `self` for the current Gitea instance.
 ;DEFAULT_ACTIONS_URL = github
-;; Logs retention time in days. Old logs will be deleted after this period.
-;LOG_RETENTION_DAYS = 365
 ;; Log compression type, `none` for no compression, `zstd` for zstd compression.
 ;; Other compression types like `gzip` are NOT supported, since seekable stream is required for log view.
 ;; It's always recommended to use compression when using local disk as log storage if CPU or memory is not a bottleneck.
 ;; And for object storage services like S3, which is billed for requests, it would cause extra 2 times of get requests for each log view.
 ;; But it will save storage space and network bandwidth, so it's still recommended to use compression.
 ;LOG_COMPRESSION = zstd
-;; Default artifact retention time in days. Artifacts could have their own retention periods by setting the `retention-days` option in `actions/upload-artifact` step.
+;; Days to keep logs. Old logs will be deleted after this period. 0 means keep forever.
+;LOG_RETENTION_DAYS = 365
+;; Days to keep artifacts. Old artifacts will be deleted after this period. 0 means keep forever.
+;; Changes only apply to newly uploaded artifacts, existing ones keep the expiry stored when they were uploaded.
+;; Artifacts could have their own retention periods by setting the `retention-days` option in `actions/upload-artifact` step.
 ;ARTIFACT_RETENTION_DAYS = 90
+;; Days to keep completed runs. Old runs and everything under them will be deleted after this period. 0 means keep forever.
+;RUN_RETENTION_DAYS = 400
 ;; Timeout to stop the task which have running status, but haven't been updated for a long time
 ;ZOMBIE_TASK_TIMEOUT = 10m
 ;; Timeout to stop the tasks which have running status and continuous updates, but don't end for a long time