[StepSecurity] Apply security best practices

.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-FROM mcr.microsoft.com/devcontainers/base:bookworm
+FROM mcr.microsoft.com/devcontainers/base:bookworm@sha256:17e6cc517b483d1108b333d4c34352b0a21617f0117052e9b259d47113a9dc37
 RUN apt-get update && \
     export DEBIAN_FRONTEND=noninteractive && \
     apt-get -y install \

.github/dependabot.yml

@@ -0,0 +1,43 @@
+version: 2
+updates:
+  - package-ecosystem: docker
+    directory: /.devcontainer
+    schedule:
+      interval: daily
+    groups:
+      all:
+          applies-to: version-updates
+          patterns:
+              - '*'
+    cooldown:
+      default-days: 5
+      include:
+          - '*'
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      all:
+          applies-to: version-updates
+          patterns:
+              - '*'
+    cooldown:
+      default-days: 5
+      include:
+          - '*'
+
+  - package-ecosystem: pip
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      all:
+          applies-to: version-updates
+          patterns:
+              - '*'
+    cooldown:
+      default-days: 5
+      include:
+          - '*'