Fix HF deployment: remove external deps, use pre-built files, download required assets

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Refactor: Remove static modifiers from AsyncContext methods and add saveFile and signDownloadUrl methods to FirebaseStorageBucketControl

Fix: Update Dockerfile to build application from source and adjust Firebase Storage stub return type

Fix: Replace private submodule with HF-compatible stubs

restructure: nolonger a firebase application (#1160)