workout-system: temporarily enable signup to bootstrap SparkyFitness admin

DISABLE_SIGNUP=true blocks OIDC auto-register too (callback returns 'Signups are
currently disabled by the administrator'), so the first admin account can't be
created. Set DISABLE_SIGNUP=false just long enough for the admin to log in via
Authentik once (auto-registers + admin via SPARKY_FITNESS_ADMIN_EMAIL); will be
reverted to true right after.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

workout-system/sparkyfitness.yaml

@@ -208,8 +208,12 @@ spec:
               value: "INFO"
             - name: SPARKY_FITNESS_FRONTEND_URL
               value: "https://workout.dooplex.hu"
+            # TEMPORARILY "false" to bootstrap the first admin account. With signup
+            # disabled, even OIDC auto-register is blocked ("Signups are currently
+            # disabled by the administrator"). Flip back to "true" immediately after
+            # the admin (SPARKY_FITNESS_ADMIN_EMAIL) has logged in via Authentik once.
             - name: SPARKY_FITNESS_DISABLE_SIGNUP
-              value: "true"
+              value: "false"
             - name: SPARKY_FITNESS_ADMIN_EMAIL
               value: "nagyfenyvesi.viktor@gmail.com"
             - name: ALLOW_PRIVATE_NETWORK_CORS