Broken click targets: error-codes 404, wrong YouTube footer, hhttps:// sample links

Several clickable links on docs.dapr.io (v1.18) are wrong:

1. https://docs.dapr.io/operations/observability/metrics/metrics-overview/ → **Dapr API error codes** → `/reference/api/error_codes/` **404**. Should be `/developing-applications/error-codes/`.

2. Footer **YouTube** → `https://www.youtube.com/@darpdev` (wrong channel). Should be `@daprdev`.

3. Secrets quickstart **JavaScript** tab → sample repo link uses `hhttps://` → `#ZgotmplZ`. Same typo on state-management **Go** tab.
4. resiliency quickstart **this** link has a trailing `//` (still 200).

Search the documentation source for the metrics overview link, YouTube footer URL, Secrets quickstart JavaScript and state-management Go sample links, and the resiliency quickstart link. Correct the four reported targets, then run the documentation link checker or build and verify that the links resolve without malformed URLs.

Written by the indexing model from the issue text.