chore: group dependency updates and pin every action by SHA

Dependabot was opening one pull request per dependency, which across this
organization produced swarms of dozens at a time. .github/dependabot.yml now
gives each ecosystem present in this repository a single catch-all group over
minor, patch and major with open-pull-requests-limit 1, so a week yields at
most one pull request per ecosystem.

Ecosystems configured: gomod(1) pip(1) docker(1) github-actions(1)

Every third-party action is now pinned to a 40-character commit SHA with its
original tag kept as a trailing comment (5 rewritten). A mutable tag like
`@v4` is repointable by whoever controls the action, so an unpinned workflow
runs whatever that tag means on the day CI happens to fire; a SHA is
immutable. The github-actions entry in dependabot.yml is what keeps those pins
moving, since nothing else would.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: antoinetoussaint-byte

.github/dependabot.yml

@@ -0,0 +1,67 @@
+# Dependency updates for every ecosystem this repository ships.
+#
+# Each ecosystem is ONE catch-all group covering minor, patch and major, with
+# open-pull-requests-limit 1, so a week yields at most one pull request per
+# ecosystem instead of one per dependency. Dependabot cannot group across
+# ecosystems, so the number of entries below is the floor on weekly PRs.
+#
+# The github-actions entry exists because every action is pinned by commit SHA;
+# nothing else would ever move those pins.
+version: 2
+
+updates:
+  - package-ecosystem: gomod
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 1
+    groups:
+      gomod:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+          - major
+
+  - package-ecosystem: pip
+    directory: /base/code
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 1
+    groups:
+      pip:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+          - major
+
+  - package-ecosystem: docker
+    directory: /templates/builder
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 1
+    groups:
+      docker:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+          - major
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 1
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+          - major

.github/workflows/ci.yml

@@ -28,8 +28,8 @@ jobs:
   race:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+      - uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
         with:
           go-version-file: go.mod
           # Same reason as the shared workflow: setup-go's cache tar corrupts

.github/workflows/releaser.yml

@@ -9,8 +9,8 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+      - uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
         with:
           go-version-file: go.mod
           # go.mod pins a `toolchain` newer than the `go` line, so setup-go
@@ -29,7 +29,7 @@ jobs:
     needs: test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
           fetch-depth: 0
       # ARCHITECTURE: the shared core release workflow runs goreleaser-action