perf: compile regex patterns once instead of per-call in hot paths

[myukitty]

Summary

Addresses #826 by compiling regular expressions once and reusing them across invocations in hot paths:

1. internal/digest/digest.go (ValidateDigest):

   • Precompiled package-level validSha256CompiledRegex instead of compiling the static SHA256 validation pattern on every call.
   • Added BenchmarkValidateDigest.

2. internal/filters/resourceFilter.go (ResourceFilterOptions):

   • Added cached compiled regex slices (compiledExclude, compiledInclude) and CompilePatterns() error method.
   • ShouldInclude compiles patterns once lazily on first invocation and reuses them across resource checks (e.g. iterating over namespaces/pods/functions/clusters).
   • Added unit tests for CompilePatterns and BenchmarkShouldInclude_Regex.

3. internal/gitview/gitView.go (MatchPatternInCommitMessageORBranchName):

   • Added MatchRegexpInCommitMessageORBranchName taking a pre-compiled *regexp.Regexp.
   • Updated MatchPatternInCommitMessageORBranchName to safely compile via regexp.Compile and delegate without panicking.
   • Added unit tests.

4. internal/jira/jira.go (FindJiraIssueKeys):

   • Precompiled static default Jira issue key pattern and dashDigitRegex.

Fixes #826.

Validation

• go test -v -run TestFiltersSuite ./internal/filters: PASS
• go test -v -run TestGitViewTestSuite ./internal/gitview: PASS
• go test -v ./internal/jira: PASS
• go test -v -run "TestDigestTestSuite/TestValidateDigest" ./internal/digest: PASS
• go test -bench=Benchmark ./internal/digest ./internal/filters: PASS
• go vet ./...: PASS (clean)
• Independent review: ATD sealed pass (APPROVE, confidence 1.0)