fix: support BGE-M3 embedding (dense_embedding fallback)

[FUYOH666]

BGE-M3 returns dense_embedding instead of embedding; ReMe expects embedding and causes TypeError: object of type 'NoneType' has no len().

This adds a fallback in _get_embeddings to use dense_embedding when embedding is None.

Related: CoPaw PR #1780 (which used a monkey-patch; this fixes the root cause in ReMe).

Made with Cursor

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[jinliyl]

LGTM