authentik: incident hardening after the signin-speedup rollout storm

The first apply of the signin-speedup change triggered a ~50min authentik
outage (and a shared CNPG primary failover): the helm chart pin (2026.2.2)
silently DOWNGRADED the Keel-managed live image (2026.2.4) against an
already-migrated DB, default liveness probes kill-looped pods queuing on
authentik's migration advisory lock, and kills mid-migration left ghost
idle-in-transaction sessions holding that lock. Full analysis in
docs/post-mortems/2026-06-10-authentik-downgrade-boot-storm.md.

Hardening (all root causes):
- values.yaml: pin global.image.tag to the Keel-managed live tag (2026.2.4)
  so helm applies can never downgrade under Keel again
- values.yaml: server livenessProbe 6x10s/5s (was chart-default 3x10s/3s)
- values.yaml: REMOVE AUTHENTIK_POSTGRESQL__CONN_MAX_AGE (session-mode
  pgbouncer pins persistent conns 1:1 -> pool saturation, 58s/s waits)
- pgbouncer.ini: idle_transaction_timeout=300 reaps ghost lock holders;
  pgbouncer.tf gets a config-checksum annotation so ini changes roll pods
- authentik_provider.tf: drop the completed import stanza (adoption rule)
- traefik: suppress pre-existing keel.sh annotation/tier-label drift on
  auth-proxy/bot-block/x402/error-pages deployments (KEEL_LIFECYCLE_V1
  pattern) so applies stop stripping live Keel state

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

stacks/authentik/modules/authentik/pgbouncer.ini

@@ -12,3 +12,7 @@ default_pool_size = 20
 reserve_pool_size = 5
 reserve_pool_timeout = 5
 ignore_startup_parameters = extra_float_digits
+; Reap server connections stuck "idle in transaction" (e.g. an authentik pod
+; killed mid-migration leaves a ghost transaction holding the migration
+; advisory lock, serializing every subsequent pod boot — 2026-06-10 incident).
+idle_transaction_timeout = 300