fix(x/auth/tx): honor deprecated Pagination in GetTxsEvent

[ozpool]

Description

Closes #25886.

GetTxsEvent only reads the top-level page, limit, and order_by fields on GetTxsEventRequest and silently drops req.pagination. REST clients hitting the gRPC-gateway endpoint typically populate pagination.limit, pagination.offset, and pagination.reverse (as in the report's URLs against /cosmos/tx/v1beta1/txs), so each request collapsed to DefaultLimit=100 ascending results regardless of the values supplied. That is the most likely explanation for the reporter seeing the same address turn up by hash / tx.height but not by transfer.recipient once the matching set exceeds 100 — they were always reading page 1 in ascending order and never reaching the missing tx.

This change keeps the deprecation in place but stops dropping the values:

• limit falls back to req.Pagination.Limit when the top-level limit is zero.
• page is derived from req.Pagination.Offset / effectiveLimit + 1, returning InvalidArgument if Offset is not a multiple of Limit (CometBFT's TxSearch is page-based).
• OrderBy_UNSPECIFIED + Pagination.Reverse=true maps to OrderBy_DESC.
• Top-level fields always win when both are populated, so existing v0.50+ clients are unaffected.

GetBlockWithTxs already reads req.Pagination directly, so this also brings GetTxsEvent in line with the sibling RPC.

Testing

New x/auth/tx/service_test.go plugs a recording TxSearch client into MockClient and exercises:

• deprecated limit honored when top-level limit is zero
• deprecated offset translated to page
• deprecated reverse mapped to desc
• top-level page/limit precedence over deprecated fields
• non-multiple offset rejected with InvalidArgument

go test ./x/auth/tx/...
ok  	github.com/cosmos/cosmos-sdk/x/auth/tx	0.661s

Author Checklist

• included the correct type prefix in the PR title
• confirmed ! in the title if this is a breaking change — n/a, additive fallback
• targeted the correct branch (main)
• provided a link to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary — n/a
• included the necessary unit tests

[greptile-apps]

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