web-app-bluesky: enable custom AppView domain and refactor DNS records

- Un-commented `view.bluesky.{{ PRIMARY_DOMAIN }}` in config to allow
  explicit AppView domain definition.
- Reworked `03_dns.yml` to build `cloudflare_records` list programmatically,
  including conditional addition of AppView records only if the domain is
  not `api.bsky.app`.
- Improved AAAA handling with `| default('')` and proper ternary
  expressions for `present/absent`.
- Updated `vars/main.yml` to remove default port fallback for
  `BLUESKY_VIEW_PORT`.

Refs: https://chatgpt.com/share/68cdde1d-1bd4-800f-a4bb-319372752fcd

roles/web-app-bluesky/config/main.yml

@@ -13,7 +13,7 @@ server:
     canonical:
       web:  "web.bluesky.{{ PRIMARY_DOMAIN }}"
       api:  "api.bluesky.{{ PRIMARY_DOMAIN }}"
-#      view: "view.bluesky.{{ PRIMARY_DOMAIN }}"
+      view: "view.bluesky.{{ PRIMARY_DOMAIN }}"
   csp:
     whitelist:
       connect-src: