…tion (#3844)

## Fix VIES Maintenance exceptions handling 

### Problem
`Valvat::MemberStateUnavailable` exceptions weren't being raised
properly, preventing fallback mechanisms from triggering when VIES is
unavailable.

Some countries won't accept requests during the weekend of after the
business hour.
Check the table here https://ec.europa.eu/taxation_customs/vies/#/help

### Solution

1. Added `raise_error: true` to Valvat calls in
`Customers::EuAutoTaxesService` to ensure exceptions are properly raised
and caught by the existing rescue block
2. Update the wait time from 30 seconds to 15.minutes, in order to avoid
overheads in the Sidekiq, since the job will run until it gets the
information.

### Next steps: 
Rethink the retry logic to make it exponential using the Sidekiq
built-in helper, or create a table with the working hours for each
country.

### Testing
- ✅ All existing tests pass
- ✅ VIES exceptions now properly trigger fallback mechanism
- ✅ Webhook notifications work correctly
- ✅ Retry job scheduling functions as expected

### Impact
Better reliability for German customers when VIES service is temporarily
unavailable, ensuring consistent tax application through proper fallback
mechanisms.

---

**Context:**
```ruby
# Before: Exception not raised
Valvat.new("DE199896394").exists?(detail: true)

# After: Exception properly raised and handled
Valvat.new("DE199896394").exists?(detail: true, raise_error: true)
```

**What happens now:**
1. When VIES is unavailable, `Valvat::MemberStateUnavailable` is
properly raised
3. Existing rescue block captures the exception
4. Webhook is sent with error details
5. Retry job is scheduled for 30 seconds later