LND Release Candidate Caps External Bitcoin Fee Estimates at 10,000 Sats/vB

Lightning Network Daemon (LND) has rolled out pre-release candidate v0.21.5-beta.rc1, establishing a 10,000 satoshis per virtual byte (sat/vB) upper ceiling on external Bitcoin fee estimates. The guardrail covers block-target estimates and the minimum relay fee rate, specifically protecting setups relying on external fee APIs, such as Neutrino light clients, without impacting local bitcoind or btcd backends. Previously, external estimates only carried a lower bound, leaving nodes exposed to upstream formatting errors or faulty third-party APIs. The update also fixes a native SQLite connection-pool deadlock bug without requiring database migrations.