ai.yaml: cut mcpo over to the confirmed-working flowagent-mcpo image + wire flowagent Docker secrets (never touches mcpo-critical)

Image pinned to git.bryanmail.net/homelab/flowagent-mcpo:916164714429 —
the exact sha-tagged image built and smoke-tested clean in mcp-config
pipeline #22 (build-and-push-flowagent + smoke-test-flowagent-image both
success). NOT :latest, for reproducible deploys.

Adds a secrets: block to the mcpo service only, referencing the 3
flowagent_azure_* Docker Swarm secrets (Pattern C, _FILE convention,
consumed by flowagent/entrypoint.sh via /run/secrets/flowagent_azure_*).
Declares those 3 secrets as external at top level, mirroring the existing
vaultwarden_admin_token_v2 pattern in vaultwarden.yaml.

Companion secret-provisioning change lands in the same PR as a separate
commit in .woodpecker/deploy.yml's provision-secrets step (case "ai)").

mcpo-critical (lines defining Proxmox access) is completely untouched —
still stock ghcr.io/open-webui/mcpo:main, no secrets: block, unchanged.

Per FlowAgent MCP progress note: Azure AD App Registration is reported
created with real secrets already in Woodpecker (both mcp-config and
compose-files repos) as of this PR. This is a reviewed PR against a
feature branch, NOT auto-merged to main — deploy only happens after
manual review/merge, per user's explicit request for a manual-revert
safety net on this high-blast-radius shared stack (LiteLLM, Open WebUI,
n8n also live here).

ai/ai.yaml

@@ -127,7 +127,7 @@ services:
       labels:
       - traefik.enable=false
   mcpo:
-    image: ghcr.io/open-webui/mcpo:main
+    image: git.bryanmail.net/homelab/flowagent-mcpo:916164714429
     command:
     - --config
     - /app/config/config.json
@@ -141,6 +141,13 @@ services:
     - /volume1/docker/mcpo/data:/mcpo_data
     - /volume1/docker/cronicle/ssh_keys:/app/ssh_keys:ro
     - /volume1/docker/mcpo/uv-cache:/app/uv-cache
+    secrets:
+    - source: flowagent_azure_client_id
+      target: flowagent_azure_client_id
+    - source: flowagent_azure_tenant_id
+      target: flowagent_azure_tenant_id
+    - source: flowagent_azure_client_secret
+      target: flowagent_azure_client_secret
     networks:
     - traefik_backend
     deploy:
@@ -173,6 +180,13 @@ services:
       - traefik.http.middlewares.n8n.headers.STSPreload=true
       - traefik.http.routers.n8n.middlewares=forwardAuth-authentik@file, crowdsec@file
       - traefik.swarm.network=traefik_backend
+secrets:
+  flowagent_azure_client_id:
+    external: true
+  flowagent_azure_tenant_id:
+    external: true
+  flowagent_azure_client_secret:
+    external: true
 networks:
   traefik_backend:
     external: true