Add proper container constraints to API documentation pages

- Added .container CSS rule to constrain content width to 1200px max-width
- Added auto margins for centering and 2rem side padding
- Now matches the layout constraints of dashboard and history pages

templates/admin_api.html

@@ -4,6 +4,7 @@
 
 {% block head %}
 <style>
+.container { max-width: 1200px; margin: 2rem auto; padding: 0 2rem; }
 .api-header {
     background: linear-gradient(135deg, #dc2626 0%, #b91c1c 100%);
     color: white;

templates/api.html

@@ -4,6 +4,7 @@
 
 {% block head %}
 <style>
+.container { max-width: 1200px; margin: 2rem auto; padding: 0 2rem; }
 .api-header {
     background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
     color: white;