test: lift coverage 78.42% → 79.59% with focused unit + integration tests
Adds tests across previously-uncovered or under-covered modules:
- Mix tasks: backfill_checks, copy_mibs, import_mibs (new test files)
- Status pages: StatusIncident changeset (new file)
- Webhook signature verification on AgentReleaseWebhookController
- CloudflareBanWorker: HTTP-stubbed success / 5xx / transport-error paths
- FirmwareVersionFetcherWorker: stubbed perform/0 success + non-200 + tx error
- Geoip.Import: production --production code path (HTTP-stubbed)
- AgentLive.Show: superuser restart_agent + update_agent + non-superuser paths
- NetworkMapLive: node_clicked, deep-link node, topology_updated PubSub
- PreseemInsightsLive: toggle_select, deselect_all, filter, dismiss-twice
- AlertQuery: 1-arity defaults variants
- ProfileWatcher: yaml + reload-trigger event passthrough
- MobileAuthController: verify_qr_token success + get/revoke session
- HealthController: redis-configured branch
- RedisHealthCheck: un-tag :integration tests now that Redis is local
- FourOhFourTracker: un-skip module (Redis available)
- PingExecutor: un-tag local-only tests + KeyError surface + clamp branch
- CheckExecutorWorker: dispatch tcp/dns/ssl/ping branches
- UserResetPasswordController: drop dead edit/update + their template
Also removes dead code: edit/update actions on UserResetPasswordController
and the unused edit.html.heex template — both routed via LiveView.