Add docs for N8N_SAMESITE_COOKIE (#3046)

Co-authored-by: Justin Ellingwood <[email protected]>

Author: elsmr

docs/hosting/configuration/environment-variables/security.md

@@ -1,7 +1,7 @@
 ---
 #https://www.notion.so/n8n/Frontmatter-432c2b8dff1f43d4b1c8d20075510fe4
 title: Security environment variables
-description: Configure authentication and environment variable access in self-hosted n8n instance. 
+description: Configure authentication and environment variable access in self-hosted n8n instance.
 contentType: reference
 tags:
   - environment variables
@@ -20,4 +20,5 @@ hide:
 | `N8N_RESTRICT_FILE_ACCESS_TO` | String |  | Limits access to files in these directories. Provide multiple files as a colon-separated list ("`:`"). |
 | `N8N_BLOCK_FILE_ACCESS_TO_N8N_FILES` | Boolean | `true` | Set to `true` to block access to all files in the `.n8n` directory and user defined configuration files. |
 | `N8N_SECURITY_AUDIT_DAYS_ABANDONED_WORKFLOW` | Number | 90 | Number of days to consider a workflow abandoned if it's not executed. |
-| `N8N_SECURE_COOKIE` | Boolean | `true` | Ensures that cookies are only sent over HTTPS, enhancing security.|
+| `N8N_SECURE_COOKIE` | Boolean | `true` | Ensures that cookies are only sent over HTTPS, enhancing security.|
+| `N8N_SAMESITE_COOKIE` | Enum string: `strict`, `lax`, `none` | `lax` | Controls cross-site cookie behavior ([learn more](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie/SameSite)):<ul><li>`strict`: Sent only for first-party requests.</li><li>`lax` (default): Sent with top-level navigation requests.</li><li>`none`: Sent in all contexts (requires HTTPS).</li></ul> |