perf: split claude-dev into base and runtime images for faster builds

- Create Dockerfile.base with all tools and dependencies (built once)
- Slim down Dockerfile to just copy scripts from base image
- CI checks for base image existence, builds if missing
- Runtime builds drop from ~17min to ~10sec (only copies scripts)
- Base image only needs rebuild when tools/versions change

.gitea/workflows/deploy-claude-dev-dev.yml

@@ -47,6 +47,18 @@ jobs:
         if: env.ROLLBACK_ONLY == '0'
         run: |
           set -euo pipefail
+          # Check if base image exists, build if missing
+          if ! docker image inspect claude-dev-base:latest >/dev/null 2>&1; then
+            echo "Base image not found, building claude-dev-base:latest..."
+            DOCKER_BUILDKIT=0 docker build \
+              -f claude-dev/Dockerfile.base \
+              -t claude-dev-base:latest \
+              claude-dev/
+          else
+            echo "Using existing claude-dev-base:latest"
+          fi
+
+          # Build runtime image (fast, just copies scripts)
           DOCKER_BUILDKIT=0 docker build \
             --cache-from claude-dev:latest \
             -t "$CLAUDE_DEV_IMAGE" \