V145: Newsletters Send Settings — phoenix_kit_newsletters_send_profiles.

Adds the send-profile table backing the newsletters module's "Send Settings" admin screen: named send configurations that reference a core Integrations connection (by integration_uuid, no FK — consistent with the codebase's loose-UUID pattern for cross-module references, see v138/v140) and carry per-account send parameters (from-name/email, reply-to, signature, rate limits, advanced per-provider extras). Multiple profiles may share one integration. At most one profile may be is_default (the service-wide default), enforced by a partial unique index.

Also adds send_profile_uuid (bare UUID, no FK) to phoenix_kit_newsletters_broadcasts, letting each broadcast pin which send profile delivers it — folded in here rather than a follow-up migration since V145 hasn't shipped anywhere yet.

All statements are idempotent, safe to re-run.