multi: bump lnd to v0.21.3-beta

[kaloudis]

chantools v0.14.x is built against lnd v0.19.0-beta, which knows channel DB schema versions up to 33. lnd v0.21.0 added version 35, so every read-write command fails on a DB last used by lnd v0.21.x:

[ERR] CHDB: Refusing to revert from db_version=35 to lower version=33
Error: error opening rescue DB: channel db cannot revert to prior version

Changes

• go.mod: lnd v0.21.3-beta, loop v0.35.0-beta (brings lndclient v0.21.0-2), pool v0.7.1-beta. Go 1.25.13 is now required (CI GO_VERSION updated).
• lnd/channeldb.go: graph DB is built with graphdb.NewKVStore and graphdb.NewChannelGraph(store).
• lnd/chanbackup.go, lnd/brontide.go: adapted to changed chanbackup, discovery.Config and peer.Config APIs. The temporary graph DB for triggerforceclose is built from a graphdb.NewKVStore.
• deletepayments: payments moved to payments/db, now uses paymentsdb.NewKVStore(...).DeletePayments.
• dropchannelgraph: graph calls take a context and gossip version. Edges are built with models.NewV1Channel (the store rejects edges without GossipVersion1). ChannelGraph.Wipe was removed upstream, so a local wipeGraph deletes graph-node, graph-edge, graph-meta and closed-scid and re-creates them, like the old lnd code did.
• lndVersion and generated docs say v0.21.3-beta.
• Test fix: the pointer address regex in root_test.go only matched 10 hex digits, so TestCompactDBAndDumpChannels failed on darwin/arm64 (also on master).
• zombierecovery_makeoffer.go: strings.Cut instead of strings.Split(...)[0]. This modernize finding also fails go tool golangci-lint run on master.

Behavior change

Read-write commands (migratedb, dropgraphzombies, dropchannelgraph, removechannel, deletepayments) now migrate older DBs to schema 35. After that the DB can't be opened by lnd older than v0.21.

Tested

• go vet ./... clean, unit tests pass (itest not run).
• go tool golangci-lint run (v2.6.2) and the v2.6.2 release binary used by CI (built with Go 1.25.3): 0 issues.
• DB created at schema 35: old binary fails with the error above, new binary runs dropgraphzombies successfully.

Tested on a real node DB

• dropgraphzombies on a channel.db from lnd v0.21.x
• dropchannelgraph (full wipe, then lnd resyncs the graph)
• dropchannelgraph --fix_only and --single_channel
• deletepayments with and without --failedonly
• chanbackup against the same DB
• triggerforceclose (uses the lnd/brontide.go peer setup)
• itest suite

Note: cmd/chantools/testdata/channel.db reports schema 20 but already contains the set-id-index bucket that migration 22 creates, so it can't be migrated read-write by either the old or the new binary. Not changed here.

Disclosure: built with assistance from Claude Opus 5.5

[guggero]

Thanks a lot for the update!
I've added some integration test coverage that actually found a small bug (see pushed commits). But now everything should be great, so LGTM 🌮