Dashboard webhooks use Svix Cloud for self-hosted Svix deployments

[igorvolocRC]

Describe the bug
Dashboard webhook management does not use the configured self-hosted Svix API URL in the browser.

The Daytona API can use SVIX_SERVER_URL for server-side Svix calls, but the dashboard does not pass a self-hosted Svix API URL to svix-react. In self-hosted or split-route deployments, browser-side webhook management can fall back to Svix Cloud (https://api.svix.com) instead of the configured self-hosted Svix instance.

To Reproduce
Steps to reproduce the behavior:

1. Deploy Daytona OSS with self-hosted Svix.
2. Configure the Daytona API with:

• SVIX_AUTH_TOKEN=...
• SVIX_SERVER_URL=http://svix.svc.cluster.local:8071

3. Expose Svix to browsers through a public/proxied URL, for example:

• https://svix.example.com

4. Open the Daytona dashboard and go to Webhooks.
5. Open the browser network tab and use the webhook management UI.
6. See browser requests go to https://api.svix.com/api/v1/... instead of the self-hosted Svix URL.

Expected behavior
The dashboard should use the browser-facing self-hosted Svix API URL for webhook management.
For split-route deployments, Daytona should support:

• Server-side API URL: SVIX_SERVER_URL=http://svix.svc.cluster.local:8071
• Browser-facing URL: SVIX_PUBLIC_SERVER_URL=https://svix.example.com
  When only SVIX_SERVER_URL=https://svix.example.com is configured, the dashboard should use that same URL.
  When no Svix server URL is configured, existing Svix Cloud behavior should remain unchanged.

Screenshots
Not applicable.

Environment (required fields):

• Deployment: OSS
• Daytona client: Dashboard
• Daytona Version: v0.184.0

Additional context
Related to #3619, which added the app portal access flow for svix-react.

The issue is specific to self-hosted Svix deployments where the Daytona API and browser may not use the same Svix route.

[Sakshi17219]

Root Cause
The Daytona API generates an app portal access token (related to issue #3619) for svix-react to use, but when constructing the svix-react component, it does not pass a serverUrl prop pointing to the self-hosted instance. svix-react therefore defaults to https://api.svix.com.

Expected Fix
The fix (addressed in PR #5079) introduces support for two environment variables:

SVIX_SERVER_URL — used by the Daytona API for internal/server-side Svix calls (already existed)
SVIX_PUBLIC_SERVER_URL (new) — the browser-facing Svix URL, passed through to svix-react

Fallback logic:

If SVIX_PUBLIC_SERVER_URL is set → use it for the dashboard
Else if SVIX_SERVER_URL is set → use it for both server and dashboard (works when the same URL is reachable by both)
If neither is set → existing Svix Cloud behavior is preserved (no regression)

Impact

Only affects self-hosted Svix deployments (OSS users with SVIX_SERVER_URL configured)
Svix Cloud users are unaffected
The bug causes webhook management in the dashboard to either fail silently or operate against the wrong Svix instance
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