DA Retrieve uses blob.GetAll (no pagination) — may fail with many blobs at one height

[randygrok]

We now retrieve DA blobs via a single blob.GetAll(height, [namespace]) call:

• block/internal/da/client.go#L203

This returns all blobs in one response (no paging/cursor in the client API):

• pkg/da/jsonrpc/client.go#L81-L120

Concern
If a height contains a very large number of blobs (e.g. ~40k), GetAll could:

• time out,
• exceed JSON-RPC response limits,
• or consume too much memory (decode all blobs at once).

[tac0turtle]

i added the pr for this in part 3