This PR collapses multiple queries fetching stats from a single table to
a single query
```sql
SELECT
user_id as user_id,
COUNT(CASE WHEN name = 'conversation_resolved' THEN 1 END) as resolved_count,
AVG(CASE WHEN name = 'conversation_resolved' THEN value END) as avg_resolution_time,
AVG(CASE WHEN name = 'first_response' THEN value END) as avg_first_response_time,
AVG(CASE WHEN name = 'reply_time' THEN value END) as avg_reply_time
FROM "reporting_events"
WHERE
"reporting_events"."account_id" = <account_id> AND
"reporting_events"."created_at" >= '2025-09-14 18:30:00' AND
"reporting_events"."created_at" < '2025-10-14 18:29:59'
GROUP BY "reporting_events"."user_id";
```
### Why this works?
Here's why this optimization is faster based on PostgreSQL internals:
- Single Table Scan vs Multiple Scans: Earlier we did 4 sequential scans
(or 4 index scans) of the same data, with the same where clause, now in
a single scan all 4 `CASE` expressions are evaluated in a single pass.
- Shared Buffer Cache Efficiency: PostgreSQL's shared buffer cache
stores recently accessed pages, with this, pages are loaded once and
re-used for all aggregation, earlier with separate queries we were
forced to re-read all from the disk each time
- Reduced planning and network overhead (4 vs 1 query)
### How is it tested
1. The specs all pass without making any changes
2. Verified the reports side by side after generating from report seeder
#### How to test
Generate seed data using the following command
```bash
ACCOUNT_ID=1 ENABLE_ACCOUNT_SEEDING=true bundle exec rake db:seed:reports_data
```
Once done download the reports, checkout to this branch and download the
reports again and compare them
a509ef826a