feat: incremental issue and pull request sync (#449)

After a complete pass, the issues and pull request passes list only the
items GitHub reports as updated since the previous listing (minus a 10
minute margin), so per-issue comment listing and per-PR detail, commits
and files calls run only for what changed. Pull requests use the issues
endpoint for this since pulls.list has no since filter.

The watermark lives in the repository metadata state as syncCursors, one
per kind, and records when the listing started. It only moves when the
pass finishes with no failed item. A full pass still runs when the last
one is older than 7 days, when the destination has no mirrored issues or
pull requests, and after reset metadata, which clears the state.

helm/gitea-mirror/Chart.yaml

@@ -2,8 +2,8 @@ apiVersion: v2
 name: gitea-mirror
 description: Kubernetes helm chart for gitea-mirror
 type: application
-version: 3.39.0
-appVersion: "3.39.0"
+version: 3.38.2
+appVersion: "3.38.2"
 icon: https://github.com/RayLabsHQ/gitea-mirror/blob/main/.github/assets/logo.png
 keywords:
   - git

package.json

@@ -1,7 +1,7 @@
 {
   "name": "gitea-mirror",
   "type": "module",
-  "version": "3.39.0",
+  "version": "3.38.2",
   "engines": {
     "bun": ">=1.2.9"
   },