Require Node.js >= 25 (engines, installers, Dockerfile, snap, CI, docs) (#7749)

* docs: bump documented Node.js minimum to 25

Etherpad is moving its supported Node.js floor to >= 25 (CI matrix is
already pinned to 25 across all workflows on the node25-corepack-pnpm11
work). Sync the user-facing documentation so the install instructions,
requirements section, and plugin metadata example all reflect the new
minimum instead of Node 22 / 12.17.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: require Node.js >= 25 (engines, installers, Dockerfile, snap, CI)

#7747 added Node 25 *support* but left the floor at Node 22. This
commit completes the cutover so the runtime requirement matches the
documentation bumped in the previous commit.

- package.json: engines.node ">=22.13.0" → ">=25.0.0"
- bin/functions.sh, bin/installer.sh, bin/installer.ps1: REQUIRED_NODE
  bumped to 25 (controls the error message users see when they invoke
  the installer or pnpm scripts on an older Node)
- Dockerfile: base image node:22-alpine → node:25-alpine (×2). Corepack
  comment updated: Node 25 no longer ships corepack at all, so we
  install it from npm rather than refreshing a stale signing-key list
- snap/snapcraft.yaml: pinned NODE_VERSION 22.22.2 → 25.9.0 and the
  surrounding design notes rewritten to reflect Node 25 instead of 22
- .github/workflows/*.yml: matrix dropped from [22, 24, 25] to just
  [25] (anything older now fails engines anyway). Stale comments in
  build-and-deploy-docs.yml referencing vite 8's 22.12 floor cleaned up
- bin/plugins/lib/npmpublish.yml: setup-node 22 → 25 so the plugin
  template propagated to every ether/* plugin matches the new minimum

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(docker): install pnpm directly on Node 25 (no corepack)

node:25-alpine doesn't ship corepack but does pre-install yarn at
/usr/local/bin/yarn, so `npm install -g corepack@latest` fails with
EEXIST trying to register its yarn shim. Per #7747, end-users install
pnpm via plain `npm install -g pnpm` on Node 25 — use the same flow in
the Dockerfile (and remove the unused yarn binary so it doesn't sit on
PATH inside the image). Drops COREPACK_HOME and the related
issue-7687 cache-sharing tweak since there's no corepack shim to share.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/backend-tests.yml

@@ -27,8 +27,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # PRs: test on latest Node only. Push to develop: full matrix.
-        node: ${{ github.event_name == 'pull_request' && fromJSON('[25]') || fromJSON('[22, 24, 25]') }}
+        # Etherpad requires Node >= 25 (see package.json engines.node).
+        node: ${{ fromJSON('[25]') }}
     steps:
       -
         name: Checkout repository
@@ -101,7 +101,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: ${{ github.event_name == 'pull_request' && fromJSON('[25]') || fromJSON('[22, 24, 25]') }}
+        node: ${{ fromJSON('[25]') }}
     steps:
       -
         name: Checkout repository

.github/workflows/build-and-deploy-docs.yml

@@ -56,8 +56,7 @@ jobs:
         with:
           run_install: false
       # Pin Node so the build does not silently fall back to whatever the
-      # runner image ships with. vite 8 requires Node ^20.19.0 || >=22.12.0;
-      # the repo declares engines.node >=22.12.0 to match.
+      # runner image ships with. The repo declares engines.node >=25.0.0.
       - name: Use Node.js
         uses: actions/setup-node@v6
         with:

.github/workflows/frontend-admin-tests.yml

@@ -21,8 +21,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # PRs: single Node version. Push: full matrix.
-        node: ${{ github.event_name == 'pull_request' && fromJSON('[25]') || fromJSON('[22, 24, 25]') }}
+        # Etherpad requires Node >= 25 (see package.json engines.node).
+        node: ${{ fromJSON('[25]') }}
 
     steps:
       -

.github/workflows/upgrade-from-latest-release.yml

@@ -27,8 +27,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # PRs: single Node version. Push: full matrix.
-        node: ${{ github.event_name == 'pull_request' && fromJSON('[25]') || fromJSON('[22, 24, 25]') }}
+        # Etherpad requires Node >= 25 (see package.json engines.node).
+        node: ${{ fromJSON('[25]') }}
     steps:
       -
         name: Check out latest release