chore: purge retired git.tx1138.com registry host from the codebase

The tx1138 Gitea was retired as a release server 2026-06-13 and its registry
frontend is fully dead (500 on every /v2 manifest read, observed 2026-07-10).
Nothing may reference it anymore:

- registry.rs: no longer a default registry, no longer force-enabled on
  load; saved configs are stripped of it on load (same one-time migration
  treatment as the decommissioned Hetzner mirror), with a regression test.
- image_policy.rs: removed from TRUSTED_REGISTRIES — refs through the dead
  host are now refused at the pull site (rejection test added).
- api/handler: dropped the legacy catalog-proxy fallback URL.
- .gitmodules: indeedhub submodule repointed to the OVH Gitea.
- scripts, image-recipe, app-catalog data, neode-ui strings, docs, and all
  test fixtures repointed to 146.59.87.168:3000 (or neutral example hosts).
- image-versions.sh: ARCHY_REGISTRY_FALLBACK emptied (guarded consumers
  skip it); reconcile-containers.sh candidate guard hardened.

The only remaining occurrences of the host string are the strip/reject
enforcement paths and their regression tests — the code that guarantees it
is never used again.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/image-versions.sh

@@ -11,7 +11,8 @@
 
 # Archipelago app registries (primary + fallback)
 ARCHY_REGISTRY="146.59.87.168:3000/lfg2025"
-ARCHY_REGISTRY_FALLBACK="git.tx1138.com/lfg2025"
+# No fallback registry: the old tx1138 registry host was retired (2026-06-13); empty disables the fallback path.
+ARCHY_REGISTRY_FALLBACK=""
 
 # Bitcoin stack
 BITCOIN_KNOTS_IMAGE="$ARCHY_REGISTRY/bitcoin-knots:latest"