Fix bundled aMule EC password synchronization

[floze-the-genius]

Summary

• derive the bundled aMule ECPassword hash from the same AMULE_PASSWORD plaintext used by the backend
• update persisted amule.conf files on startup so password rotations do not leave the daemon and EC client out of sync
• keep devcontainer generation and Compose documentation aligned with the runtime behavior
• add regression coverage for default, custom, and rotated passwords

Verification

• tests/entrypoint-config.test.sh
• sh -n entrypoint.sh
• bash -n .devcontainer/setup-amule.sh
• docker build -t mularr-batch70-typescript-02:fixed .
• clean-volume container with AMULE_PASSWORD=custom-secret: /api/media/transfers succeeded and generated ECPassword=ddc33abcbec51fd4de296be5cf1230fe
• persisted-volume rotation from the old hardcoded hash to custom-secret: /api/media/transfers succeeded with no EC authentication errors

On current main (v0.16.2), the default secret path already authenticates successfully. The remaining reproducible failure was setting AMULE_PASSWORD, which changed the backend credential while generated and persisted bundled configs retained the hardcoded hash for secret.

Fixes #20

[Copilot]

Pull request overview

This PR fixes aMule ExternalConnect (EC) authentication mismatches by ensuring the bundled amuled and the backend derive credentials from the same AMULE_PASSWORD plaintext, and by updating persisted amule.conf files on startup so password rotations don’t leave EC client/daemon out of sync.

Changes:

• Derive ECPassword (MD5 hash) from AMULE_PASSWORD in entrypoint.sh (defaulting to secret) and write it into generated configs.
• On startup, synchronize ECPassword in an existing persisted amule.conf to match the current AMULE_PASSWORD.
• Add a shell regression test covering default, custom, and rotated password scenarios; align devcontainer + Compose documentation with runtime behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/entrypoint-config.test.sh	Adds regression coverage for default/custom/rotated EC password hashing and persistence behavior.
entrypoint.sh	Computes EC password hash from AMULE_PASSWORD and synchronizes persisted amule.conf on startup.
docker-compose.example.yml	Updates documentation comments to reflect that AMULE_PASSWORD configures both bundled aMule and Mularr.
.devcontainer/setup-amule.sh	Uses the same AMULE_PASSWORD-derived EC password hash when generating dev configs.

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