fix: propagate kubectl error in GetPodsforDeployment, compile regexp once

[immanuwell]

What this PR does / why we need it:

Two small fixes:

1. GetPodsforDeployment was silently dropping the error from kubectl get deployment. When kubectl fails you'd get a confusing unexpected end of JSON input instead of the actual error. One-liner fix - just stop ignoring the err.

2. SanitizeName was calling regexp.MustCompile on every invocation. The regex is constant so it should be compiled once at package level (same pattern already used in account.go right next door).

Bonus: trimmed a stray trailing space off an error string in CheckVersionIncrement.

How to reproduce:

For (1): call GetPodsforDeployment with a deployment name that doesn't exist or when kubectl isn't configured - you'll see unexpected end of JSON input instead of the real kubectl error.

For (2): SanitizeName is called in CreateInstallParams for every chart install, so the regex gets recompiled on each run. No functional impact but wasteful.

Special notes for your reviewer:

All existing tests pass, no behavior change for (2) and (3), (1) now surfaces the real error earlier.