cli: show multicast group codes in feed list

[bgm-malbeclabs]

Resolves: malbeclabs/infra#2172

Summary of Changes

• doublezero feed list gains a group_codes column naming the multicast groups the feed holds, so the list answers "what's in this feed?" without a follow-up feed get plus manual pubkey lookups.
• Groups are resolved to codes via one list_multicastgroup call; a group the ledger no longer carries falls back to its raw pubkey, matching how accesspass list renders its allowlists.
• The existing groups count column is unchanged, and the JSON output gains the new field (additive — existing consumers that decode a field subset, including the feed_crud e2e test, are unaffected).

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	1	+17 / -1	+16
Tests	1	+75 / -0	+75
Docs	1	+3 / -0	+3
Total	2	+95 / -1	+94

A one-column display change; most of the diff is the new list test.

Key files (click to expand)

• smartcontract/cli/src/feed/list.rs — adds the group_codes field to FeedDisplay, resolves group pubkeys to codes with a pubkey fallback, and adds test_cli_feed_list covering both the resolved and unknown-group paths
• CHANGELOG.md — Unreleased / Changes entry under CLI

Testing Verification

• New test_cli_feed_list asserts the rendered table carries the column and that a feed holding one known and one unknown group renders mg01, 11111115q4Ep… — the code for the resolved group, the raw pubkey for the other.
• Rendered output confirmed by hand: account | code | name | exchange | groups | group_codes | owner.
• cargo test -p doublezero-serviceability-cli feed:: — 34 passing.