Remove API key copy and move to kernel login

[heyglassy]

Description

Please provide an explanation of the changes you've made:

Implementation Checklist

• Implemented this change in TypeScript
• Implemented this change in Python

Testing

• All tests pass locally
• Linted
• Added tests for new functionality (if applicable)

Docs

• Link to a PR in our docs repo documenting your change (if applicable)

Visual Proof

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Related Issue

Fixes [Github issue link]

Additional Notes

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TL;DR

Updated all sample applications and CLI instructions to use kernel login for authentication instead of manually setting KERNEL_API_KEY environment variables.

Why we made these changes

To simplify and standardize the user authentication process, making it more user-friendly and consistent across all Kernel sample applications and documentation. This centralizes API key management and improves the developer experience.

What changed?

• README.md: Updated API key setup instructions to suggest kernel login and improved general markdown formatting.
• Core CLI Instructions (index.ts): Refactored string literals and conditional statements; updated printNextSteps to guide users towards kernel login.
• Python Templates (templates/python/*/*.py): Modified main.py files in advanced-sample, cua, and sample-app to remove direct KERNEL_API_KEY environment variable usage, directing users to kernel login.
• TypeScript Templates (templates/typescript/*/*.ts): Updated index.ts files in advanced-sample, cua, and sample-app comments and CLI invocation instructions to reflect the kernel login command. sample-app also received extensive code reformatting and consistent use of double quotes for strings.

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[masnwilliams]

so on our docs, we moved to kernel login but kept the api key route as a note, is there a good way to do that so people know its still an option?

heres what im referencing: https://docs.onkernel.com/quickstart#3-authenticate-with-kernel

[masnwilliams]

lgtm