refactor(base): SimpleLogin's forwarding page on the OpenID Connect module (ADR 0023)

halkyon_base depends on halkyon_oidc_server, and its forwarding page
is now the module's (`addOidcCallbackForwarding`) with Halkyon's table
of apps and its page in English or German; its tests keep what is
Halkyon's own, the rest is tested in the module.

Every host now includes the module: migrations `…-oidc-module` in
halkyon_base, Learn and Todo create its two tables (no data touched)
and record its version; Learn's devices get them empty, as they have
halkyon_base's server-only tables. halkyon_base_client depends on
halkyon_oidc_client, whose models its generated code uses, and Learn's
server image copies both packages into its narrowed workspace.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_server/migrations/migration_registry.txt

@@ -46,3 +46,4 @@
 20261021134803749-reset-hold-outs
 20261021184601197-private-studysets
 20261023131636437
+20261023181810112-oidc-module