feat: add automated backporting to release branches

.backportrc.json

@@ -0,0 +1,8 @@
+{
+  "branchLabelMapping": {
+    "^backport-to-(release/.+)$": "$1"
+  },
+  "prTitle": "{commitMessages} (backport to {targetBranch})",
+  "targetPRLabels": ["backport"],
+  "autoMerge": false
+}

.github/BACKPORT.md

@@ -0,0 +1,39 @@
+# Backporting to release branches
+
+Backports merged `main` changes onto long-term `release/*` branches as PRs.
+Config lives in `.backportrc.json` and is shared by both methods below.
+
+## Immediate (one PR)
+
+Add a label `backport-to-release/<branch>` to the PR (before or after merge),
+e.g. `backport-to-release/1.14.x`. On merge, the Backport workflow opens a
+backport PR to that branch. Add multiple labels to fan out to several branches.
+A clean cherry-pick opens the PR automatically; a conflict instead comments on
+the source PR (finish it with the CLI below).
+
+> The label must exist before you can apply it. When labeling for a new branch
+> the first time, create the label (the labels box offers "Create new label").
+
+## Batch (many PRs at once)
+
+One-time local auth: create `~/.backport/config.json` with
+`{ "accessToken": "<a GitHub token with repo scope>" }`.
+
+Then gather and select interactively (targets passed at runtime, so any
+`release/*` works without editing config):
+
+```bash
+# By query, then arrow-key multi-select the PRs:
+npx backport --pr-query "merged:>=2026-05-01 label:backport-pending" \
+  --branch release/1.15.0 --branch release/1.14.x
+# Or by path / single PR:
+npx backport --path en/use-dify --branch release/1.14.x
+npx backport --pr 792 --branch release/1.14.x
+```
+
+## Finishing a conflicting backport
+
+```bash
+npx backport --pr <source-pr-number> --branch release/<branch>
+# resolve the conflict when prompted; the CLI pushes and opens the PR
+```

.github/workflows/backport.yml

@@ -0,0 +1,16 @@
+name: Backport merged PR
+on:
+  pull_request_target:
+    types: [labeled, closed]
+permissions:
+  contents: read
+  pull-requests: read
+jobs:
+  backport:
+    if: github.event.pull_request.merged == true
+    runs-on: depot-ubuntu-24.04
+    steps:
+      - uses: sorenlouv/backport-github-action@v12
+        with:
+          github_token: ${{ secrets.BACKPORT_TOKEN }}
+          auto_backport_label_prefix: backport-to-

.mintignore

@@ -13,3 +13,9 @@
 # Non-public utility files under public asset directories
 /assets/migrate_weaviate_collections.py
 /logo/convertor.html
+
+# Internal contributor runbooks
+/.github/BACKPORT.md
+
+# Backport tooling config
+/.backportrc.json