chore(ci): complete the backport label rename across all consumers

The initial rename missed several literal consumers of the old label
names beyond labels.yml and backport.yaml:

- stale.yaml exempt-pr-labels still listed backport,backport-previous.
  actions/stale matches label names exactly and does not resolve
  label-sync aliases, so after the rename a kind/backport PR would lose
  its stale exemption and get auto-closed after inactivity. This is the
  one behavioural regression; the rest are documentation drift.
- PULL_REQUEST_TEMPLATE.md told contributors to apply the backport label.
- release.md label-target table and the gh pr list --search commands
  referenced the old names (the searches would silently return nothing).
- contributing.md claimed a backport label is auto-applied on the
  [Backport] prefix; pr-labeler only adds area/release, so the line was
  already stale and is corrected while renaming.

Historical narrative in release.md and the backport scope-to-area doc
rows (a Conventional-Commit scope, not the label) are left as-is.

Signed-off-by: IvanHunters <xorokhotnikov@gmail.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,7 +8,7 @@
   - Breaking changes: append `!` after type/scope (`feat(api)!: ...`) or add a `BREAKING CHANGE:` footer
 - If it's a work in progress, consider creating this PR as a draft.
 - Don't hesistate to ask for opinion and review in the community chats, even if it's still a draft.
-- Add the label `backport` if it's a bugfix that needs to be backported to a previous version.
+- Add the label `kind/backport` if it's a bugfix that needs to be backported to a previous version.
 -->
 
 ## What this PR does

.github/workflows/stale.yaml

@@ -39,7 +39,7 @@ jobs:
             triage/accepted,kind/regression
           exempt-pr-labels: >-
             lifecycle/frozen,do-not-merge/hold,
-            backport,backport-previous
+            kind/backport,kind/backport-previous
           days-before-stale: 60
           days-before-close: 14
           operations-per-run: 100

docs/agents/contributing.md

@@ -105,7 +105,7 @@ git commit --signoff -m "docs(contributing): add installation guide"
 
 **Special handling:**
 
-- `[Backport release-1.x]` prefix is stripped before parsing; `area/release` and `backport` labels are added.
+- `[Backport release-1.x]` prefix is stripped before parsing; the `area/release` label is added.
 - Composite scope (`feat(platform, system, apps): ...`) — each comma-separated part is mapped independently.
 - `!` after type or `BREAKING CHANGE:` footer in the body → `kind/breaking-change`.
 - Unmapped scope or non-conventional title → `area/uncategorized` (signals the PR needs manual area selection).

docs/release.md

@@ -282,8 +282,8 @@ The matching Talos node image is `ghcr.io/cozystack/cozystack/cozystack-nocloud:
 
 | Label | Target branch |
 |-------|---------------|
-| `backport` | `release-X.Y` (current latest minor) |
-| `backport-previous` | `release-X.(Y-1)` |
+| `kind/backport` | `release-X.Y` (current latest minor) |
+| `kind/backport-previous` | `release-X.(Y-1)` |
 
 Resolution is dynamic via `getLatestRelease` at run time — no need to hardcode branch names.
 
@@ -309,7 +309,7 @@ git push origin release-X.Y  # or push to a new branch and open a PR
 To find the bot's failed comments across a batch of PRs:
 
 ```bash
-for n in $(gh pr list --search "label:backport label:backport-previous merged:>=2026-01-01" --json number --jq '.[].number'); do
+for n in $(gh pr list --search "label:kind/backport label:kind/backport-previous merged:>=2026-01-01" --json number --jq '.[].number'); do
   echo "=== #$n ==="
   gh pr view $n --json comments --jq '.comments[] | select(.author.login == "github-actions" or (.author.login | contains("backport"))) | .body' | head -20
 done
@@ -321,8 +321,8 @@ A patch release includes bugfixes for code that shipped in the corresponding min
 
 ```bash
 # 1. Inventory PRs already labeled for backport (merged but not yet on release-X.Y)
-gh pr list --search "is:merged label:backport" --limit 100
-gh pr list --search "is:merged label:backport-previous" --limit 100
+gh pr list --search "is:merged label:kind/backport" --limit 100
+gh pr list --search "is:merged label:kind/backport-previous" --limit 100
 
 # 2. List commits on main since the release branch diverged that are NOT yet on release-X.Y
 git merge-base origin/main origin/release-X.Y