List notifications

Two sources in one list, newest first: what the memory editor learned (kind: "memory_operation") and the notices the product writes, the end of an import (kind: "memory_ready", with deep_link to the conversation and read) and the daily dating reminder (kind: "dating_cooling", no contact and no names by design, deep_link: "/app/dating"). Ids come from two tables, so a stable client key is the pair (kind, id).