feat: prompt admin with PKCE client support hint (#1499)

Co-authored-by: james <james@goldfish.net>
Co-authored-by: Alessandro (Ale) Segala <43508+ItalyPaleAle@users.noreply.github.com>
Co-authored-by: Elias Schneider <login@eliasschneider.com>
Co-authored-by: Kyle Mendell <kmendell@ofkm.us>

backend/resources/migrations/sqlite/20260726153900_add_pkce_supported_to_oidc_clients.down.sql

@@ -0,0 +1,7 @@
+PRAGMA foreign_keys=OFF;
+BEGIN;
+
+ALTER TABLE oidc_clients DROP COLUMN pkce_supported;
+
+COMMIT;
+PRAGMA foreign_keys=ON;

backend/resources/migrations/sqlite/20260726153900_add_pkce_supported_to_oidc_clients.up.sql

@@ -0,0 +1,8 @@
+PRAGMA foreign_keys= OFF;
+BEGIN;
+
+ALTER TABLE oidc_clients
+	ADD COLUMN pkce_supported BOOLEAN NOT NULL DEFAULT 0;
+
+COMMIT;
+PRAGMA foreign_keys= ON;