smartcontract,client: add topology CLI commands

[ben-malbeclabs]

RFC-18 flex-algo · PR 2 of 5 · see rfcs/rfc-0018-flex-algo.md
Depends on: #3497 (PR 1)
Series: #3497 · #3512 · #3513 · #3514 · #3515

Summary of Changes

• Adds five doublezero link topology subcommands: create, delete, clear, list, backfill
• Backs each with a Rust SDK command in doublezero_sdk::commands::topology
• topology list displays name, admin-group bit, flex-algo number, BGP color community, constraint, and linked link count
• topology clear removes a topology from all links that reference it; topology backfill allocates flex-algo node segments on all activated devices for a given topology
• Wires the link topology subcommand group into the existing doublezero link command tree

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	11	+1334 / -0	+1334
Scaffolding	6	+84 / -6	+78

Heavy on new code — all five CLI commands and six SDK commands are new files with no prior equivalent.

Key files (click to expand)

• smartcontract/cli/src/topology/list.rs — lists all TopologyInfo accounts; shows BGP color (128 + admin_group_bit), constraint, and how many links are tagged with each topology
• smartcontract/cli/src/topology/clear.rs — removes a topology from all links that reference it; confirms or dry-runs before submitting transactions
• smartcontract/cli/src/topology/create.rs — creates a topology with name, constraint (include-any or exclude); admin-group bit and flex-algo number are allocated automatically onchain
• smartcontract/cli/src/topology/backfill.rs — calls BackfillTopology for a named topology, optionally scoped to specific device pubkeys
• smartcontract/sdk/rs/src/commands/topology/backfill.rs — SDK command for BackfillTopology; includes unit tests with mock client
• smartcontract/sdk/rs/src/commands/topology/list.rs — SDK command for listing topology accounts; includes unit tests

Testing Verification

• cargo test -p doublezero_sdk -p doublezero_cli passes
• cargo clippy -- -D warnings clean
• make rust-fmt applied before commit