refactor: move payment gateway settings to payment settings page and hide API...

refactor: move payment gateway settings to payment settings page and hide API Tokens for config admin

- Moved payment gateway configuration (Stripe, PayPal, crypto) from admin tiers page to admin payment settings page
- Removed payment gateway HTML section (lines 115-290) from admin_tiers.html
- Removed payment gateway JavaScript functions from admin_tiers.html
- Added payment gateway section to admin_payment_settings.html with all 6 gateways (PayPal, Stripe, BTC, ETH, USDT, USDC)
- Added loadPaymentGateways() and savePaymentGateways() functions to admin_payment_settings.html
- Hide 'API Tokens' navigation link for config admin user (user_id is null for config admin)
- API Tokens link now only shows for database users (request.session.user_id exists)
- Config admin defined in aisbf.json has no user_id, so they won't see API Tokens link
- Admin tiers page now focuses only on tier management and currency settings
- Admin payment settings page now has all payment configuration in one place

templates/base.html

@@ -502,7 +502,9 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
             <a href="{{ url_for(request, '/dashboard/autoselect') }}" {% if '/autoselect' in request.path %}class="active"{% endif %}>Autoselect</a>
             <a href="{{ url_for(request, '/dashboard/prompts') }}" {% if '/prompts' in request.path %}class="active"{% endif %}>Prompts</a>
             <a href="{{ url_for(request, '/dashboard/analytics') }}" {% if '/analytics' in request.path %}class="active"{% endif %}>Analytics</a>
+            {% if request.session.user_id %}
             <a href="{{ url_for(request, '/dashboard/user/tokens') }}" {% if '/user/tokens' in request.path %}class="active"{% endif %}>API Tokens</a>
+            {% endif %}
             {% if request.session.role == 'admin' %}
             <a href="{{ url_for(request, '/dashboard/users') }}" {% if '/users' in request.path %}class="active"{% endif %}>Users</a>
             <a href="{{ url_for(request, '/dashboard/settings') }}" {% if '/settings' in request.path %}class="active"{% endif %}>Settings</a>