docs: use app.posthog.com for remaining feature-preview links (fixes part of #13516)

Two docs pages still linked to us.posthog.com for the feature previews
settings page, which redirects EU users through the US region. 14 other
docs pages already use the region-neutral app.posthog.com host; standardise
these two to match.

Author: singhvishalkr

contents/docs/alerts/index.mdx

@@ -158,7 +158,7 @@ Percentage thresholds are only available for relative alerts (as you need to com
 
 <CalloutBox icon="IconFlask" title="Feature preview" type="info">
 
-Anomaly detection alerts are in **beta**. To enable them, go to [Settings > Feature previews](https://us.posthog.com/settings/user-feature-previews) and toggle on **Anomaly Detection Alerts**.
+Anomaly detection alerts are in **beta**. To enable them, go to [Settings > Feature previews](https://app.posthog.com/settings/user-feature-previews) and toggle on **Anomaly Detection Alerts**.
 
 </CalloutBox>
 

contents/docs/cdp/sources/incoming-webhooks.mdx

@@ -11,7 +11,7 @@ import { ProductScreenshot } from 'components/ProductScreenshot'
 
 <CalloutBox icon="IconInfo" title="Feature preview" type="caution">
 
-Incoming webhook sources are experimental and available behind a [feature preview](https://us.posthog.com/settings/user-feature-previews#cdp-hog-sources). For most use cases, we recommend using a [workflow with a webhook trigger](/docs/workflows/workflow-builder#webhook-triggers) combined with a **capture event** action instead — it's more flexible, doesn't require code, and gives you access to delays, branching, and other workflow features.
+Incoming webhook sources are experimental and available behind a [feature preview](https://app.posthog.com/settings/user-feature-previews#cdp-hog-sources). For most use cases, we recommend using a [workflow with a webhook trigger](/docs/workflows/workflow-builder#webhook-triggers) combined with a **capture event** action instead — it's more flexible, doesn't require code, and gives you access to delays, branching, and other workflow features.
 
 </CalloutBox>