Inconsistent rate limiting between v2 and v3 data-download/raw-data endpoints

# Inconsistent rate limiting between v2 and v3 data-download/raw-data endpoints

## Summary
v3 `/data-download` and `/raw-data` are rate-limited at 10/min; the v2 equivalents have no rate limiting at all. Unclear whether this gap is intentional.

## Where this came from
Baalmart, following up on AirQo-frontend PR #3876's data-download review, tracing the request path in `src/analytics`.

## Affected code
- v3 rate limiting — `views/v3/data.py:49,98`
- v2 endpoints (no rate limiting found)

## Suggested fix
Confirm which API version the nexus frontend actually calls, and either apply the same rate-limit policy to v2 or confirm the gap is intentional (e.g. v2 is deprecated/internal-only) and document it.

## Acceptance criteria
- [ ] Confirmed which version nexus calls for data-download/raw-data
- [ ] Rate limiting is consistent across v2/v3, or the discrepancy is deliberate and documented

Start with AirQo-frontend PR #3876 and trace the nexus frontend request path to confirm which API version it uses for data-download and raw-data. Compare the v3 rate limits in views/v3/data.py at lines 49 and 98 with the v2 endpoints, then verify that the final policy is either consistent across versions or explicitly documented as intentional.

Escrito por el modelo de indexación a partir del texto del issue.