v0.2.1 — CI / test infrastructure fixes + dep bump

Patch release. No product behaviour changes — CI / test infrastructure
fixes plus one dependency bump caught while shipping v0.2.0.

Fixed

• Test infrastructure: pinned in-memory SQLite to a single connection
  (db.SetMaxOpenConns(1)) in mission and supervisor tests. The
  database/sql connection pool was handing fresh empty :memory:
  databases to runtime poll goroutines under -race + heavy parallel
  CI load, causing "no such table" flakes that masquerade as test
  timeouts. Locally the Go scheduler hid the bug; on Linux CI it
  surfaced reliably. (74c3610, 1ca121b)

Dependencies

• Bumped github.com/pelletier/go-toml/v2 from 2.3.0 to 2.3.1
  (Dependabot, PR #2).

Other

• Enabled Dependency Graph + vulnerability alerts on the repo. Future
  Dependabot PRs no longer fail the Dependency Review Action.