align V1ReferralsResource with cached resource pattern

[PabloDinella]

• refactor V1ReferralsResource to follow the same tenant-scoped model/caching approach used by other resources
• consolidate V1 referral contracts/events/model/resource code into the standard resource layout
• move command application logic into V1ReferralModel and keep V1Referral as a read model/contract
• reduce repeated full event-log scans on read paths (GetReferralAsync / ListReferralsAsync)
• preserve append-only command execution and deterministic replay using persisted event audit data
• extract V1 referral notes into a standalone V1ReferralNotes resource, matching the family notes pattern
• update DI and records wiring for the V1Referrals and V1ReferralNotes resources