fix(analytics): use "Requests" instead of "Downloads" where technically appropriate

Problem

The analytics UI currently uses the term Downloads throughout. For cloud-native formats (COGs, Zarr, GeoParquet, PMTiles, etc.), users access data via HTTP range requests — not full file downloads. A single "download" of a large COG may generate hundreds of HTTP 206 (partial content) range requests.

Labeling all access as "Downloads" is misleading:

• It implies users retrieved entire files, which is often not the case.
• It understates actual usage (a dataset accessed heavily via range requests looks like zero downloads).
• It conflates two meaningfully different access patterns that the data proxy already distinguishes via `status_code` (200 vs 206).

Proposed Change

Use Requests (or a context-appropriate equivalent) as the primary label for HTTP access counts, reserving Downloads only for cases where a full file transfer is confirmed (HTTP 200, no range request).

Suggested terminology

The proxy already captures `status_code`, so the data needed to split these is available (see #257).

References

• #257 — the analytics feature where both terms appear; the 200 vs 206 split is called out in the V1 proposal but the UI label was never revisited.

Start by reviewing the analytics feature in #257 and tracing how the analytics UI consumes the data proxy's status_code values. Update the terminology so total HTTP access is shown as Requests, full HTTP 200 transfers as Downloads, and HTTP 206 access as Range requests; verify the relevant analytics views and counts distinguish these cases.