Add buys query table from exchange_to_wallet events

Denormalized read table with id, event_id, occurred_at, wallet, sats,
fee_sats, and amount_eur. Projected on event creation and rebuildable
via POST /api/buys/rebuild. Fiat amounts converted to EUR using
Frankfurter rates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

resources/migrations/20260316000000-create-buys.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS buys;

resources/migrations/20260316000000-create-buys.up.sql

@@ -0,0 +1,7 @@
+CREATE TABLE buys (
+  id          BIGSERIAL PRIMARY KEY,
+  event_id    BIGINT NOT NULL REFERENCES events(id) UNIQUE,
+  occurred_at DATE NOT NULL,
+  wallet      TEXT NOT NULL,
+  amount_eur  NUMERIC(18,2) NOT NULL
+);

resources/migrations/20260316100000-buys-add-sats.down.sql

@@ -0,0 +1,3 @@
+ALTER TABLE buys DROP COLUMN fee_sats;
+--;;
+ALTER TABLE buys DROP COLUMN sats;

resources/migrations/20260316100000-buys-add-sats.up.sql

@@ -0,0 +1,3 @@
+ALTER TABLE buys ADD COLUMN sats BIGINT NOT NULL DEFAULT 0;
+--;;
+ALTER TABLE buys ADD COLUMN fee_sats BIGINT;

resources/queries.sql

@@ -155,6 +155,30 @@ SELECT id, event_id, occurred_at, exchange, fiat_amount, fiat_currency,
 FROM deposits
 ORDER BY occurred_at DESC, id DESC
 
+-- :name truncate-buys! :! :n
+-- :doc Delete all rows from the buys read table
+TRUNCATE buys
+
+-- :name get-buy-events :? :*
+-- :doc Get exchange_to_wallet events with wallet name, oldest first
+SELECT e.id, e.occurred_at, e.sats, e.fee_sats, e.fiat_amount, e.fiat_currency,
+       e.to_wallet_id, tw.name AS wallet
+FROM events e
+LEFT JOIN wallets tw ON tw.id = e.to_wallet_id
+WHERE e.event_type = 'exchange_to_wallet'
+ORDER BY e.occurred_at ASC, e.id ASC
+
+-- :name insert-buy! :! :n
+-- :doc Insert a projected buy row
+INSERT INTO buys (event_id, occurred_at, wallet, sats, fee_sats, amount_eur)
+VALUES (:event-id, :occurred-at, :wallet, :sats, :fee-sats, :amount-eur)
+
+-- :name get-all-buys :? :*
+-- :doc Get all projected buys ordered by date descending
+SELECT id, event_id, occurred_at, wallet, sats, fee_sats, amount_eur
+FROM buys
+ORDER BY occurred_at DESC, id DESC
+
 -- :name get-kraken-hour-latest-24 :? :*
 -- :doc Get the 24 most recent Kraken hourly candles
 SELECT ts, open, high, low, close, vwap, volume, trade_count, created_at