Add namespace validation to catch invalid names before build/deploy

[RayyanSeliya]

Changes

• 🎁 Add early namespace validation with user-friendly error messages
• 🐛 Prevent wasted build time when using invalid namespace names
• 🧹 Add comprehensive unit tests for namespace validation

Adds DNS-1123 validation for namespace names before build/deploy operations. Invalid namespace names now fail immediately with clear error messages instead of proceeding through lengthy builds.

Implementation:

• Add ValidateNamespace() function using Kubernetes DNS-1123 validation (pkg/utils/names.go)
• Add validation check in deployConfig.Validate() and error handling in runDeploy() (cmd/deploy.go)
• Add ErrInvalidNamespace error type (pkg/functions/errors.go) with user-friendly CLI message

/kind enhancement

Fixes #3132

Release Note

Invalid namespace names are now caught immediately with helpful error messages, preventing wasted build time

[knative-prow]

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[knative-prow]

Hi @RayyanSeliya. 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.

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[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.01%. Comparing base (b990215) to head (3a6126d).

Files with missing lines	Patch %	Lines
cmd/deploy.go	5.26%	16 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3133      +/-   ##
==========================================
+ Coverage   58.31%   59.01%   +0.69%     
==========================================
  Files         134      134              
  Lines       17377    17404      +27     
==========================================
+ Hits        10134    10271     +137     
+ Misses       6302     6162     -140     
- Partials      941      971      +30     

Flag	Coverage Δ
e2e-tests	40.19% <11.11%> (+1.29%)	⬆️
integration-tests	53.83% <3.70%> (+1.56%)	⬆️
unit-tests	46.20% <33.33%> (-0.03%)	⬇️

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[RayyanSeliya]

Hey @gauron99 can u have alook when u have some moments am I doing right ?