feat(tradein/db): user_events table — unified login/IP audit + behavior event log (#2515)

Append-only user_events table (event_type, username, ip_address inet, user_agent, path, method, estimate_id, payload jsonb, created_at) + 4 indexes. Foundation for login/IP audit + behavior analytics. Resurrects dropped audit_log design.

tradein-mvp/backend/data/sql/184_user_events.sql

@@ -0,0 +1,60 @@
+-- 184_user_events.sql
+-- Foundation schema for Features 2 & 3: unified user-event tracking.
+--
+-- WHY:
+--   trade-in had no durable event log for login/IP audit or behavior
+--   analytics. A near-identical design already existed once — `audit_log`
+--   (event_type, ip_address inet, user_agent, estimate_id uuid, payload
+--   jsonb, created_at) was defined in 002_core_tables.sql and DROPPED in
+--   095_dead_schema.sql as unused dead schema at the time. Product now
+--   needs exactly that shape again, so this migration resurrects the
+--   design under a new name, `user_events`, as the ONE unified
+--   append-only table serving:
+--     - login-audit (who logged in, from what IP/UA, when)
+--     - search-audit (estimate requests, listing lookups)
+--     - behavior-analytics (pdf_download, listing_click, page_view,
+--       drawer_open, and future event_type values)
+--
+-- WHAT:
+--   `user_events` — append-only, admin-read-only. No 152-ФЗ consent
+--   gating and no mandatory retention policy for MVP (product-owner
+--   decision): we log IP/UA/path/method/payload unconditionally for every
+--   tracked event. `estimate_id` is a plain uuid column with NO FK
+--   constraint on purpose — this keeps the log decoupled/append-only so
+--   estimate deletion (or any future estimate lifecycle change) never
+--   blocks or cascades into event rows.
+--
+-- IDEMPOTENCY / SAFETY:
+--   CREATE TABLE IF NOT EXISTS + CREATE INDEX IF NOT EXISTS throughout —
+--   safe re-run. Purely additive: no existing table/view/column is
+--   touched.
+--
+-- Dependencies: none (new standalone table). Auto-applied on deploy via
+-- _schema_migrations tracking (tradein-mvp/backend/data/sql convention).
+
+BEGIN;
+
+CREATE TABLE IF NOT EXISTS user_events (
+    id           bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    event_type   text NOT NULL,
+    username     text NOT NULL,
+    ip_address   inet,
+    user_agent   text,
+    path         text,
+    method       text,
+    estimate_id  uuid,
+    payload      jsonb NOT NULL DEFAULT '{}'::jsonb,
+    created_at   timestamptz NOT NULL DEFAULT now()
+);
+
+COMMENT ON TABLE user_events IS 'Unified append-only event log (login/IP audit + behavior analytics), admin-read-only. Resurrects the design of audit_log (002_core_tables.sql, dropped in 095_dead_schema.sql).';
+COMMENT ON COLUMN user_events.event_type IS 'e.g. login / estimate_request / pdf_download / listing_click / page_view / drawer_open.';
+COMMENT ON COLUMN user_events.username IS 'X-Authenticated-User value at the time of the event.';
+COMMENT ON COLUMN user_events.estimate_id IS 'No FK constraint by design — keeps the log decoupled/append-only from trade_in_estimates lifecycle.';
+
+CREATE INDEX IF NOT EXISTS user_events_username_created_at_idx ON user_events (username, created_at DESC);
+CREATE INDEX IF NOT EXISTS user_events_event_type_created_at_idx ON user_events (event_type, created_at DESC);
+CREATE INDEX IF NOT EXISTS user_events_ip_address_idx ON user_events (ip_address);
+CREATE INDEX IF NOT EXISTS user_events_created_at_idx ON user_events (created_at DESC);
+
+COMMIT;