fix(hosts): clean docker rows on delete

[simonjcarr]

Summary

• delete Docker inventory and telemetry dependants before hard-deleting a host
• preserve real SSH authentication failures while reporting non-auth SSH connection errors separately
• add focused regression coverage for both paths

Root cause

Host deletion did not clear the newer Docker tables that reference hosts, so deleting hosts with Docker status or telemetry could fail on foreign key constraints. The terminal websocket also defaulted all SSH open failures to SSH authentication failed, which hid DNS/network/session errors behind a misleading password error.

Validation

• node --test apps/web/lib/actions/agents-delete-hard.test.mjs
• go test ./apps/ingest/internal/handlers ./apps/ingest/internal/db/queries
• pnpm --filter web type-check