fix: resolve architecture warnings (SVC-006, FE-008, FE-004)

- Move db.commit() from admin_subscription_service to API endpoints
- Add noqa comments for intentional number inputs in templates
- Add noqa comment for inline modal in subscriptions.html

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/templates/admin/subscription-tiers.html

@@ -1,4 +1,5 @@
 {# app/templates/admin/subscription-tiers.html #}
+{# noqa: FE-008 - Using raw number inputs for cents/limits in admin tier config modal #}
 {% extends "admin/base.html" %}
 {% from 'shared/macros/alerts.html' import alert_dynamic, error_state %}
 {% from 'shared/macros/headers.html' import page_header_refresh %}