ci: bump actions/checkout from 4 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
     name: frontend (build)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: actions/setup-node@v4
         with:
           node-version: '22'
@@ -38,7 +38,7 @@ jobs:
     name: backend (compile + package)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: actions/setup-java@v4
         with:
           distribution: temurin
@@ -54,7 +54,7 @@ jobs:
     name: mcp (syntax)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: actions/setup-node@v4
         with:
           node-version: '22'
@@ -68,7 +68,7 @@ jobs:
     name: docker compose build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       # Catches the case where the code compiles but the image does not. Our
       # distribution path is "clone and build", so an unbuildable image is a
       # total outage for a new user even when every test passes.
@@ -112,7 +112,7 @@ jobs:
           --health-timeout 5s
           --health-retries 10
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: actions/setup-java@v4
         with:
           distribution: temurin
@@ -146,7 +146,7 @@ jobs:
     name: frontend lint (advisory)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: actions/setup-node@v4
         with:
           node-version: '22'

.github/workflows/codeql.yml

@@ -37,7 +37,7 @@ jobs:
           - language: java-kotlin
           - language: javascript-typescript
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v3