release: bump Keep to v0.5.0

[kwsantiago]

Bumps the bundled Keep to v0.5.0.

Changes

• Points the keep submodule at the keep v0.5.0 release (8d7d3a4).
• Version graph: the initial 0.4.8:1 moves to versions/v0_4_8.ts (retained in other), and current becomes 0.5.0:0. The upgrade is a no-op migration (Keep is a binary update with no on-disk schema change; downgrade IMPOSSIBLE).

What this brings to StartOS users

• Multi-node availability: keep-state replication over a Nostr relay, with a shared cluster vault data key, for high-availability multi-node operation.
• Core security hardening: RNG health-check failures now fail closed instead of panicking; TLS certificate pinning supports multiple pins per host for safe rotation; a corrected post-refresh group-key check; PSBT prevout amounts validated against a chain view before signing; and cryptographic dependencies advanced past recent RUSTSEC advisories.

(v0.5.0 also adds CLI/desktop features, threshold-OPRF unlock, software DKG, HD FROST wallets, that are not surfaced in the StartOS package UI; they are noted here only for completeness.)

Verification

npm run check (tsc) passes, and make builds a clean keep_x86_64.s9pk (33M, start-sdk 1.5.3) from the v0.5.0 submodule.