feat: update rental document templates to remove doctype declaration

feat: add model for lease endings as dated facts with immutable records

docs/adr/0016-model-lease-endings-as-dated-facts.md

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+# Model lease endings as dated facts
+
+**Status**: accepted
+
+Lease endings are represented by immutable, audited facts owned by `Lease`: a standard furnished lease has no real end until a tenant notice is recorded, while a student lease retains its fixed nine-month end. Tenant notices freeze the legal rule and calculated notice period that applied when received; agreed early endings, accepted withdrawals, administrative invalidations, evidence versions, and closure confirmations are appended without erasing history. Operational labels such as notice in progress, awaiting closure, and unauthorized occupancy are derived from those facts and civil dates rather than persisted as additional lease statuses or advanced by a scheduler.
+
+A known contract end immediately bounds apartment occupancy and unpaid rent dues, including a prorated final month, while confirmed payments remain correctable only through the existing explicit reversal workflow. Closure after the contract end and key return is the sole transition to `ARCHIVED`; it neither clears outstanding debts nor prevents later settlement of existing dues. A successor lease may be finalized without date overlap before the former lease is closed, but any later withdrawal or correction that would create overlap is rejected. Landlord-issued notices, tenant notices for shared leases, security-deposit settlement, exit inspections, and occupancy compensation remain outside this increment.