Disable PKCE on ecosplay_code client (Gitea compat)

Gitea 1.25.5 and earlier do not send PKCE code_challenge_method
on OIDC sources, so enforcing PKCE in Keycloak causes:

  Missing parameter: code_challenge_method

at the /auth endpoint. Drop the pkce.code.challenge.method
attribute from the ecosplay_code client block in the realm
import JSON, and add a set_client_pkce helper to sync.sh that
clears the attribute on existing installs. All other clients
(ecosplay_web, eticket) keep S256.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

realms/ecosplay-realm.json

@@ -120,7 +120,7 @@
     {
       "clientId": "ecosplay_code",
       "name": "E-Cosplay Code",
-      "description": "Forge de code (Gitea) - login SSO via ecosplay_code provider",
+      "description": "Forge de code (Gitea) - login SSO via ecosplay_code provider (Gitea ne supporte pas PKCE)",
       "enabled": true,
       "publicClient": false,
       "secret": "change-me-in-admin-console",
@@ -139,8 +139,7 @@
       "serviceAccountsEnabled": false,
       "frontchannelLogout": true,
       "attributes": {
-        "post.logout.redirect.uris": "https://code.e-cosplay.fr/*##https://cos.local/*",
-        "pkce.code.challenge.method": "S256"
+        "post.logout.redirect.uris": "https://code.e-cosplay.fr/*##https://cos.local/*"
       }
     },
     {