feat: add DB queries for ai_gateway_coderd_keys (#25564)

Adds Insert, List and Delete queries for `ai_gateway_coderd_keys `
table.

coderd/database/queries/ai_gateway_keys.sql

@@ -0,0 +1,13 @@
+-- name: InsertAIGatewayKey :one
+INSERT INTO ai_gateway_keys (id, name, secret_prefix, hashed_secret, created_at)
+VALUES ($1, @name, $2, $3, NOW())
+RETURNING id, name, secret_prefix, created_at;
+
+-- name: ListAIGatewayKeys :many
+SELECT id, name, secret_prefix, created_at, last_used_at
+FROM ai_gateway_keys
+ORDER BY created_at ASC;
+
+-- name: DeleteAIGatewayKey :one
+DELETE FROM ai_gateway_keys WHERE id = $1
+RETURNING id, name, secret_prefix, created_at, last_used_at;