Revert "feat: add OIDC tables and update federation cache for improved token management"

This reverts commit 379772d94e.

docs/DATABASE_SCHEMA.md

@@ -107,15 +107,3 @@ Schema truth is `migrations/*.sql`. This file is compact human map of current DB
 - No route-optimization/routing tables
 - No audit table for intervention link access beyond `last_accessed_at`
 - Containment check for admin area polygons is simple vertex-inside check
-
-## OIDC Tables
-- `oidc_authentications`
-  login transaction state, provider snapshot, callback/result lifecycle
-- `oidc_authentication_tokens`
-  authorization code and tokens tied to `oidc_authentications`
-- `oidc_federation_cache`
-  cached federation documents with expiry; uniqueness enforced by generated
-  SHA-256 `cache_key` over `(document_type, issuer, subject, fetch_url)` to stay
-  within MySQL index limits
-- `user_external_identities`
-  external provider subject linkage and merged claims snapshot

migrations/011_oidc_rp_foundation.sql

@@ -67,19 +67,16 @@ CREATE TABLE IF NOT EXISTS oidc_federation_cache (
     issuer VARCHAR(255) NOT NULL,
     subject VARCHAR(255) NULL,
     fetch_url VARCHAR(500) NOT NULL,
-    cache_key BINARY(32) GENERATED ALWAYS AS (
-        UNHEX(
-            SHA2(
-                JSON_ARRAY(document_type, issuer, subject, fetch_url),
-                256
-            )
-        )
-    ) STORED,
     payload_json JSON NOT NULL,
     expires_at DATETIME NOT NULL,
     created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
     updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
-    UNIQUE KEY oidc_federation_cache_unique (cache_key),
+    UNIQUE KEY oidc_federation_cache_unique (
+        document_type,
+        issuer,
+        subject,
+        fetch_url
+    ),
     KEY oidc_federation_cache_expires_idx (expires_at)
 );