Tag inactive pull requests as stale (#1993)

## Description:

Adds a new action to check pull requests every day. If there hasn't been
any action taken in three weeks, the PR gets the `stale` label. Replaces
#1183 and should help with #962.
This action uses a `start date` so that already-existing PRs aren't
affected.

**Before Merging** there should be a discussion: do we want to add
labels indicating who PRs are waiting on? We could add `waiting on
triage` & `waiting on author`/`waiting on OP`, and use actions to
add/remove those labels.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

loymdayddaud

---------

Co-authored-by: evanpelle <evanpelle@gmail.com>

.github/workflows/pr-stale.yml

@@ -0,0 +1,22 @@
+name: 🧼 Stale PR Check
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/stale@8f717f0dfca33b78d3c933452e42558e4456c8e7
+        with:
+          days-before-close: 14
+          days-before-stale: 14
+          exempt-draft-pr: true
+          exempt-pr-assignees: evanpelle
+          stale-pr-label: "stale"
+          stale-pr-message: "This pull request is stale because it has been open for 14 days with no activity. If you want to keep this pull request open, add a comment or update the branch."
+          start-date: 2025-09-03T00:00:00+00:00