fix(deploy): provision the certs dir traversable by the nonroot gateway

The Ansible base-directory loop created /opt/scrabble/certs at mode 0750
(deploy:deploy), like config/dumps/images. The gateway (and backend) run as
the distroless nonroot UID 65532 — not the deploy user — so the container
cannot traverse a 0750 certs dir and fails at startup with
"mtls: load server keypair: ... permission denied", crash-looping.

This is latent: a long-running container holds the keypair in memory and
never re-reads the file, so the misconfig only bites when a container
restarts (a host reboot / redeploy). A hoster maintenance reboot exposed it
on prod — the gateway came back crash-looping while the deploy could not SSH
in mid-reboot.

Split certs out of the 0750 loop and create it 0755 (traversable). The keys
stay 0644 by design (the gateway compose relies on it); the host is
single-tenant + SSH-access-controlled, so a traversable certs dir adds no
meaningful exposure. The live prod host was already chmod-fixed by hand; this
keeps the next provisioning run from re-tightening it.

deploy/ansible/roles/common/tasks/main.yml

@@ -213,6 +213,20 @@
   loop:
     - ""
     - config
-    - certs
     - dumps
     - images
+
+# The certs dir holds the reverse-mTLS bot-link keypair, bind-mounted into the gateway (and
+# backend) which run as the distroless nonroot UID 65532 — not the deploy user. The dir must be
+# traversable by "other" (0755) or the nonroot process cannot open the 0644 keypair and crash-loops
+# at startup ("mtls: load server keypair: ... permission denied") — a latent failure that only bites
+# on a container restart (e.g. a host reboot), not while a long-running container holds the keypair
+# in memory. The keys themselves are 0644 by design (see the gateway compose); the host is
+# single-tenant and SSH-access-controlled, so a traversable certs dir adds no meaningful exposure.
+- name: Create the scrabble certs directory (traversable by the nonroot gateway UID)
+  ansible.builtin.file:
+    path: "{{ scrabble_base_dir }}/certs"
+    state: directory
+    owner: "{{ deploy_user }}"
+    group: "{{ deploy_user }}"
+    mode: "0755"