bump to 0.3.2+v5.1.0

Wire up the file-upload conversion path that CONVERSION_UPLOAD_ENABLED
exposes:

- Add Y_PROVIDER_API_BASE_URL and Y_PROVIDER_API_KEY_FILE to common-env
  so the backend can call y-provider (used for .md→Yjs).
- Add DOCSPEC_API_URL to common-env and a new docspec service
  (ghcr.io/docspecio/api:3.0.1) for the .docx→BlockNote→Yjs path.

These were missing because they were dormant while
CONVERSION_UPLOAD_ENABLED defaulted to false upstream. Now that the
recipe defaults it to true (0.3.1+v5.1.0), they're required for the
upload endpoint to function.

Upstream reference:
- https://github.com/suitenumerique/docs/blob/v5.1.0/compose.yml (docspec service)
- https://github.com/suitenumerique/docs/blob/v5.1.0/env.d/development/common (DOCSPEC_API_URL, Y_PROVIDER_API_BASE_URL)
- https://github.com/docspecio/api (DocSpec source)

compose.yml

@@ -209,7 +209,7 @@ services:
       - backend
     healthcheck:
       # /health is a proper GET endpoint returning 200 "Healthy."
-      # Use 127.0.0.1: the Elixir app binds IPv4 only, "localhost" resolves to ::1 first and fails.
+      # Use 127.0.0.1, which is required instead of localhost for this healtcheck because of elixir/busybox bindings
       test: ["CMD", "wget", "-q", "-O", "/dev/null", "http://127.0.0.1:4000/health"]
       interval: 15s
       timeout: 5s