feat(traefik): migrate keepalived password to manifest-driven Pattern C provisioning

Root cause of the 2026-09-12 VIP instability incident: traefik/traefik.env
was committed to git with a literal "***REDACTED***" placeholder as
KEEPALIVED_PASSWORD. Every git-guard resync/checkout restored that broken
value onto disk, diverging from keepalived-backup's stale-but-correct
in-memory value and causing a continuous VRRP auth failure + VIP flapping.

- Adds TRAEFIK_KEEPALIVED_PASSWORD (from_secret: traefik_keepalived_password)
  to provision-secrets environment block
- Replaces the traefik legacy case-entry (previously grouped with
  maintenance|media|unifi|... as "no Docker secrets, host .env only") with
  a call to deploy/provision-stack.py traefik, matching the ai) stack's
  manifest-driven pattern
- traefik/traefik.env is now rendered fresh from traefik/traefik.env.template
  on every provisioning run and never committed to git again

Diffed $${ occurrence count against previous version before committing,
per this file's own 2026-08-26 incident note.

.woodpecker/deploy.yml

@@ -70,6 +70,16 @@ when:
 #   tolerating a failing stack-ps in verify (|| true) so a genuinely missing
 #   stack produces the designed WARNING instead of killing the step. This
 #   hazard was first flagged in July (PR #3, closed unmerged).
+#
+#   2026-09-12 MIGRATION: traefik moved from Pattern B (secrets hand-typed
+#   into the host-only traefik.env, no CI involvement at all) to the same
+#   manifest-driven provisioning as ai) below. Root cause of the migration:
+#   traefik.env had been accidentally committed to git with a literal
+#   "***REDACTED***" placeholder as KEEPALIVED_PASSWORD; every git-guard
+#   resync/checkout silently restored that broken value, which diverged from
+#   keepalived-backup's stale-but-correct in-memory value and produced a
+#   continuous VRRP auth failure ("received an invalid passwd!") and VIP
+#   instability. The manifest-driven path never commits the rendered file.
 # ─────────────────────────────────────────────────────────────────────────────
 
 steps:
@@ -216,6 +226,11 @@ steps:
         from_secret: flowagent_azure_tenant_id
       FLOWAGENT_AZURE_CLIENT_SECRET:
         from_secret: flowagent_azure_client_secret
+      # ── traefik stack (manifest-driven — secrets/secrets-map.yaml +
+      #    traefik/traefik.env.template + deploy/provision-stack.py).
+      #    Migrated 2026-09-12; see header note above for root cause. ──
+      TRAEFIK_KEEPALIVED_PASSWORD:
+        from_secret: traefik_keepalived_password
     commands:
       - apk add --no-cache openssh-client python3 py3-yaml
       - mkdir -p ~/.ssh
@@ -243,8 +258,19 @@ steps:
         for STACK in $ALL_STACKS; do
           echo "Provisioning: $STACK"
           case "$STACK" in
-            maintenance|media|unifi|guacamole|security|auth|traefik|meshcentral|ddm)
+            maintenance|media|unifi|guacamole|security|auth|meshcentral|ddm)
               echo "  No Docker secrets for $STACK — secrets in host .env";;
+            traefik)
+              # MIGRATED (2026-09-12) to manifest-driven provisioning after
+              # discovering traefik.env was committed to git with a literal
+              # "***REDACTED***" placeholder as KEEPALIVED_PASSWORD — every
+              # git-guard resync/checkout restored the broken value, causing
+              # VRRP auth mismatch between keepalived-master/-backup and VIP
+              # instability. All logic lives in deploy/provision-stack.py;
+              # the authoritative key list lives in
+              # traefik/traefik.env.template; the mapping lives in
+              # secrets/secrets-map.yaml. This case is intentionally one line.
+              python3 deploy/provision-stack.py traefik;;
             immich)
               ssh -o StrictHostKeyChecking=no root@$${SWARM_MANAGER_IP} "source /tmp/cs.sh
                 create_or_update_secret 'immich_db_password'     '$${IMMICH_DB_PASSWORD}'