chore(cloud): remove migrated and unused projects

[mlhiter]

What this PR does

• remove migrated frontend providers and their monorepo build, workspace, Helm, and development references
• remove migrated DevBox and object storage controllers plus retired DevBox and MinIO services
• keep the remaining MinIO consumers working by constructing their clients directly
• retain the bucket-size compatibility API consumed by the migrated object storage controller
• update controller/service module detection, cloud install inputs, active frontend documentation, and generated dependency metadata

Verification

• git diff --check upstream/release-v5.1...HEAD
• bash -n deploy/cloud/init.sh scripts/cloud/install-v2.sh scripts/detect-build-modules.sh
• go run github.com/rhysd/actionlint/cmd/actionlint@v1.7.7 .github/workflows/frontends.yml
• pnpm install --frozen-lockfile --ignore-scripts
• GOFLAGS=-mod=readonly go test -run '^$' ./... in controllers/pkg, controllers/account, and controllers/resources
• GOFLAGS=-mod=readonly go test ./pkg/... in service
• compile sealos-apps/objectstorage:main against the updated local controllers/pkg module
• Helm lint and template rendering for all seven remaining frontend chart modules

Full integration tests that require MongoDB, CockroachDB, MinIO, Stripe, or the Kubebuilder test control plane were not run locally. The corresponding packages compile successfully with readonly module metadata; GitHub CI remains the Linux integration gate.