Add ESLint support for Node.js templates

[intojhanurag]

What this PR does

• Adds ESLint to Node.js templates (http and cloudevents).
• Adds a lint script to each template's package.json.
• Updates the Makefile check-node target to run npm ci && npm run lint for both templates.
• Integrates Node.js linting into make check-templates alongside Go and Rust template checks.

Notes

• No other dependencies were upgraded.
• Node.js engine warnings are ignored (current Node v22 is higher than the package requirement).

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: intojhanurag
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[knative-prow]

Hi @intojhanurag. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.68%. Comparing base (252a2ce) to head (80dcf7c).

❗ There is a different number of reports uploaded between BASE (252a2ce) and HEAD (80dcf7c). Click for more details.

HEAD has 5 uploads less than BASE

Flag	BASE (252a2ce)	HEAD (80dcf7c)
	1	0
unit-tests	3	0
integration-tests	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3134       +/-   ##
===========================================
- Coverage   59.37%   41.68%   -17.70%     
===========================================
  Files         134      117       -17     
  Lines       13500    13050      -450     
===========================================
- Hits         8016     5440     -2576     
- Misses       4540     6781     +2241     
+ Partials      944      829      -115     

Flag	Coverage Δ
e2e-tests	41.68% <ø> (+1.46%)	⬆️
integration-tests	?
unit-tests	?

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[intojhanurag]

Hey @lkingland , it is ready for review.