smartcontract: update device interface IPs on link tunnel_net change

[elitegreg]

Closes #3361

Summary of Changes

• When UpdateLink changes tunnel_net, the device interface IPs on both sides are now recalculated from the new tunnel_net, matching the existing behavior in ActivateLink
• The UpdateLink instruction now accepts optional device accounts (side_a, side_z) when tunnel_net is being updated, in both onchain and legacy allocation modes
• The SDK automatically includes the device accounts when tunnel_net is provided

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	2	+72 / -5	+67
Tests	1	+19 / -0	+19

~80% of the diff is core logic (processor + SDK); the rest is test assertions.

Key files (click to expand)

• smartcontract/programs/doublezero-serviceability/src/processors/link/update.rs — add optional device account parsing and interface IP update logic after tunnel_net change
• smartcontract/programs/doublezero-serviceability/tests/link_onchain_allocation_test.rs — pass device accounts in tunnel_net update test, assert interface IPs match new tunnel_net
• smartcontract/sdk/rs/src/commands/link/update.rs — include link's side_a/side_z device accounts when tunnel_net is being updated

Testing Verification

• Extended test_update_link_tunnel_reallocation_with_onchain_allocation to pass device accounts and assert that both device interface IPs are updated to match the new tunnel_net (10.100.0.10/31 → side_a gets 10.100.0.10/31, side_z gets 10.100.0.11/31)
• All 13 link onchain allocation tests pass
• All link WAN and DZX tests pass (7 total)
• make rust-fmt and make rust-lint clean

[juan-malbeclabs]

LGTM