refactor(queries): replace hardcoded event types with constants

Replaced hardcoded `event_type` values with named constants from
`EVENT_TYPE`, as in #3614. Added the `BOUNCE_THRESHOLD` constant and
documented it in `docker-compose.yml`.

src/queries/sql/sessions/getWebsiteSession.ts

@@ -49,8 +49,8 @@ async function relationalQuery(websiteId: string, sessionId: string) {
           session.city,
           min(website_event.created_at) as min_time,
           max(website_event.created_at) as max_time,
-          sum(case when website_event.event_type = 1 then 1 else 0 end) as views,
-          sum(case when website_event.event_type = 2 then 1 else 0 end) as events
+          sum(case when website_event.event_type = ${EVENT_TYPE.pageView} then 1 else 0 end) as views,
+          sum(case when website_event.event_type = ${EVENT_TYPE.customEvent} then 1 else 0 end) as events
     from session
     join website_event on website_event.session_id = session.session_id
     where session.website_id = {{websiteId::uuid}}