Call ensure_embedding_dimension after running migrations for tenant
schemas. This ensures the embedding column dimension matches the
model's dimension, which may differ from the default 384 dimensions
used in the initial migration.
Without this fix, using embedding providers with different dimensions
(e.g., Cohere's embed-english-v3.0 with 1024 dims) would fail with
"expected 384 dimensions, not 1024" errors on tenant schemas.
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