refactor: drop shared-service meta dependencies from service roles

podman, postgres, valkey, and nginx are shared services deployed once
per host. Declaring them in meta/main.yml re-ran them on every service
deploy, adding significant time to targeted runs. Playbooks now list
shared services first (tagged 'infra') and every role entry carries a
group tag plus its own name, so '--tags <role>' deploys just that role.

Roles still fail fast when a shared service is missing (password
asserts, postgresql tasks). Prerequisites are documented in role
READMEs. CLAUDE.md updated to reflect the new convention.

roles/fdroid/meta/main.yml

@@ -1,3 +1,5 @@
 ---
-dependencies:
-  - role: podman
+# No meta dependencies: shared services (podman) are deployed once via
+# playbook role ordering (tagged 'infra'), not re-run on every deploy of
+# this role. See playbooks/*.yml.
+dependencies: []