feat(infra): enforce MFA on the medewerker realm (refs #132)

Every seeded medewerker carries a TOTP credential, so Keycloak's conditional-OTP
step in both the browser and direct-grant flows always challenges them; a password
alone no longer yields a token. CONFIGURE_TOTP becomes a default required action so
any medewerker added later must enrol before logging in.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

infra/keycloak/realms/medewerker-realm.json

@@ -2,6 +2,16 @@
   "realm": "medewerker",
   "enabled": true,
   "displayName": "Medewerkers",
+  "requiredActions": [
+    {
+      "alias": "CONFIGURE_TOTP",
+      "name": "Configure OTP",
+      "providerId": "CONFIGURE_TOTP",
+      "enabled": true,
+      "defaultAction": true,
+      "priority": 10
+    }
+  ],
   "roles": {
     "realm": [
       { "name": "behandelaar", "description": "Behandelt registratieaanvragen" },
@@ -43,7 +53,15 @@
       "lastName": "Behandelaar",
       "email": "merel@big.example.nl",
       "emailVerified": true,
-      "credentials": [{ "type": "password", "value": "test123", "temporary": false }],
+      "credentials": [
+        { "type": "password", "value": "test123", "temporary": false },
+        {
+          "type": "otp",
+          "userLabel": "seeded TOTP (fixture)",
+          "secretData": "{\"value\":\"BIGMEDEWERKEROTPSEED\"}",
+          "credentialData": "{\"subType\":\"totp\",\"digits\":6,\"counter\":0,\"period\":30,\"algorithm\":\"HmacSHA1\"}"
+        }
+      ],
       "realmRoles": ["behandelaar"]
     },
     {
@@ -53,7 +71,15 @@
       "lastName": "Teamlead",
       "email": "tom@big.example.nl",
       "emailVerified": true,
-      "credentials": [{ "type": "password", "value": "test123", "temporary": false }],
+      "credentials": [
+        { "type": "password", "value": "test123", "temporary": false },
+        {
+          "type": "otp",
+          "userLabel": "seeded TOTP (fixture)",
+          "secretData": "{\"value\":\"BIGMEDEWERKEROTPSEED\"}",
+          "credentialData": "{\"subType\":\"totp\",\"digits\":6,\"counter\":0,\"period\":30,\"algorithm\":\"HmacSHA1\"}"
+        }
+      ],
       "realmRoles": ["behandelaar", "teamlead"]
     },
     {
@@ -63,7 +89,15 @@
       "lastName": "Beheerder",
       "email": "bram@big.example.nl",
       "emailVerified": true,
-      "credentials": [{ "type": "password", "value": "test123", "temporary": false }],
+      "credentials": [
+        { "type": "password", "value": "test123", "temporary": false },
+        {
+          "type": "otp",
+          "userLabel": "seeded TOTP (fixture)",
+          "secretData": "{\"value\":\"BIGMEDEWERKEROTPSEED\"}",
+          "credentialData": "{\"subType\":\"totp\",\"digits\":6,\"counter\":0,\"period\":30,\"algorithm\":\"HmacSHA1\"}"
+        }
+      ],
       "realmRoles": ["beheerder"]
     }
   ]