feat: add generic rclone backup destinations

[jhhjwei]

/claim #416

Summary

Adds a provider-neutral custom rclone destination while preserving the existing S3 flow.

• adds Custom rclone remote to backup destination settings
• accepts a named rclone remote such as gdrive: / onedrive: or an on-the-fly connection string such as :sftp,host=example.com,user=alice:
• supports an optional remote base path
• reuses the same destination builder for connection tests, database backups, compose backups, web-server backups, and retention cleanup
• shell-quotes every generated destination argument and redacts passwords, tokens, secrets, and access keys from logs/errors
• keeps all existing S3 providers and credentials behavior unchanged
• updates backup logs to say “destination” instead of “S3”
• fixes the streaming backup path so database dumps are no longer executed twice before upload

This enables Google Drive, OneDrive, FTP, SFTP, and other rclone-supported backends without adding provider-specific database columns.

Validation

• pnpm --filter @dokploy/server typecheck
• pnpm --filter dokploy typecheck
• Biome check on changed files
• git diff --check

Notes

For OAuth-backed remotes such as Google Drive and OneDrive, a named remote already configured on the Dokploy host can be used. For stateless providers such as FTP and SFTP, an rclone connection string can be supplied directly.

[jhhjwei]

Implementation and validation are complete. I also added shell-safe quoting for custom rclone targets and credential redaction for connection strings and provider-specific password/token flags.

Both server and app TypeScript checks pass, along with Biome and git diff --check.

The upstream workflow runs currently show action_required, which appears consistent with first-time contributor workflow approval. @Siumauricio, please approve the Actions runs when reviewing this PR. I will address any review feedback directly on this branch.

[jhhjwei]

/claim #416