docs: update api step 1 path in self hosting documentation

[cubic-dev-local]

## What does this PR do?

In Step 1 of the API section (https://cal.com/docs/self-hosting/installation#api), the instructions currently tell users to create a .env file from a path that doesn’t exist. Since the documentation is referring to API version v2, I’ve corrected the path so that the .env file is copied and created from the correct directory.

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

• Are there environment variables that should be set? No

• What are the minimal test data to have? Not needed for this pr

• What is expected (happy path) to have (input and output)? If a user follows the updated instructions they should see a .env in the apps/api/v2 path

• Any other important info that could help to test that PR? No

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  Based on: docs: update api step 1 path in self hosting documentation calcom/cal.com#23393

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Summary by cubic

Fixes the .env copy path in the self-hosting API v2 setup. The command now uses apps/api/v2/.env.example -> apps/api/v2/.env, preventing errors from a non-existent path and ensuring the env file is created in the right directory.

[github-actions]

This PR is being marked as stale due to inactivity.

[cubic-dev-ai]

No issues found across 1 file

[cubic-dev-ai]

No issues found across 1 file

[github-actions]

This PR is being marked as stale due to inactivity.