refactor(api): rename scan_frequency_minutes to scan_poll_interval_seconds

- Update API field from scan_frequency_minutes to scan_poll_interval_seconds
- Update database schema default value key
- Update Bruno API collection requests and documentation
- Update OpenAPI documentation examples and field descriptions

bruno/library/Get Scan Settings.yml

@@ -29,7 +29,7 @@ docs: |-
     **Authentication:** Required (Bearer token)
 
     **Response:**
-    - `scan_frequency_minutes` (number): Minutes between automatic scans (minimum 1)
+    - `scan_poll_interval_seconds` (number): Minutes between automatic scans (minimum 1)
     - `auto_scan_enabled` (boolean): Whether automatic scanning is enabled
     - `last_scan_at` (string, optional): Timestamp of last scan
     - `next_scan_at` (string, optional): Timestamp of next scheduled scan

bruno/library/Update Scan Settings.yml

@@ -13,7 +13,7 @@ http:
     type: json
     data: |-
       {
-        "scan_frequency_minutes": 30,
+        "scan_poll_interval_seconds": 30,
         "auto_scan_enabled": true
       }
   auth: inherit
@@ -36,7 +36,7 @@ docs: |-
     **Authentication:** Required
 
     **Request Body:**
-    - `scan_frequency_minutes` (integer, required): Minutes between automatic scans (15-1440)
+    - `scan_poll_interval_seconds` (integer, required): Minutes between automatic scans (15-1440)
     - `auto_scan_enabled` (boolean, required): Whether automatic scanning is enabled
 
     **Response:**