feat: Add Maven dependency caching to CI/CD workflows

Add actions/cache@v4 to both library-api and builder-api deployment workflows to cache Maven dependencies in ~/.m2/repository. This will significantly speed up builds by avoiding re-downloading dependencies on every run.

Changes:
- Cache key based on pom.xml hash (invalidates when dependencies change)
- Restore keys allow fallback to previous Maven cache
- Expected time savings: 1-3 minutes per deployment (40-60% faster)

Also added temporary branch triggers to test caching on this branch before merging:
- library-api: Added branch trigger for current branch
- builder-api: Added branch trigger and workflow file to paths

These temporary triggers should be removed before merging to main.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: prestoncabe

.github/workflows/deploy-builder-api.yml

@@ -7,10 +7,12 @@ on:
   push:
     branches:
       - main
+      - '227-cicd-cache-devbox-install-to-speed-up-deployment'  # TEMPORARY: Testing Maven cache
     paths:
       - 'builder-api/**'
       - 'devbox.json'
       - 'devbox.lock'
+      - '.github/workflows/deploy-builder-api.yml'  # TEMPORARY: Trigger on workflow changes
 
 env:
   PROJECT_ID: 'benefit-decision-toolkit-play'
@@ -43,6 +45,15 @@ jobs:
         with:
           enable-cache: true
 
+      # Cache Maven dependencies to speed up builds
+      - name: 'Cache Maven dependencies'
+        uses: 'actions/cache@v4'
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('builder-api/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
+
       # Configure Workload Identity Federation and generate an access token
       - id: 'auth'
         name: 'Authenticate to Google Cloud'

.github/workflows/deploy-library-api.yml

@@ -7,6 +7,8 @@ on:
   push:
     tags:
       - 'library-api-v*'
+    branches:
+      - '227-cicd-cache-devbox-install-to-speed-up-deployment'  # TEMPORARY: Testing Maven cache
 
 env:
   PROJECT_ID: 'benefit-decision-toolkit-play'
@@ -37,6 +39,15 @@ jobs:
         with:
           enable-cache: true
 
+      # Cache Maven dependencies to speed up builds
+      - name: 'Cache Maven dependencies'
+        uses: 'actions/cache@v4'
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('library-api/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
+
       # Extract version from pom.xml (source of truth) using Maven
       - name: 'Extract version from pom.xml'
         id: extract_version