PostgreSQL reconnect retry interval should be configurable

## Description

When a PostgreSQL connection is lost, Drogon automatically attempts to
reconnect every 1 second.

This can cause unnecessary CPU usage, connection attempts, and excessive
logs when PostgreSQL is unavailable for an extended period.

I am using Drogon v1.9.13.

## Current behavior

In `orm_lib/src/DbClientImpl.cc`, the reconnect is scheduled with:

```cpp
loop->runAfter(1, [weakPtr, loop, closeConnPtr] {
...
});
```
As a result, when PostgreSQL is down, I see logs like:

```
Pg connection failed
Pg connection failed
Pg connection failed
Pg connection failed
```

approximately every second for each connection in the pool.

Expected behavior

It would be useful to have a configurable reconnect interval, for example:

`"reconnect_interval": 5`

The default could remain 1 second for backward compatibility.

Suggested implementation

Instead of hard-coding:

```cpp
loop->runAfter(1, [weakPtr, loop, closeConnPtr] {
...
});
```

the reconnect delay could be stored in the database client configuration:

```cpp
loop->runAfter(reconnectInterval, [weakPtr, loop, closeConnPtr] {
...
});
```
This would allow applications with unstable or remote PostgreSQL servers to
use a more appropriate retry interval.

Thanks!

Start in orm_lib/src/DbClientImpl.cc at the hard-coded one-second runAfter reconnect scheduling, then trace how database client configuration is stored and read. Make the reconnect interval configurable while preserving a one-second default, and verify that PostgreSQL reconnect attempts use the configured value.

Written by the indexing model from the issue text.