feat: dispatch-parity quality improvements

[jongio]

Dispatch-Parity Quality Improvements

Brings azd-app CI/CD and code quality to parity with jongio/dispatch.

CI/CD & Security

• SHA-pinned all GitHub Actions to immutable commit SHAs
• Added CODEOWNERS with @jongio
• Added CodeQL security scanning workflow
• Added govulncheck vulnerability scanning workflow
• Added Dependabot for Go modules and GitHub Actions
• Added cosign code signing and SBOM generation to release workflow
• Added concurrency control to CI workflows

Code Quality

• Upgraded golangci-lint config to proper v2 format (30+ linters)
• Migrated from v1 config format (settings were silently ignored) to proper v2 nested format
• Added deadcode detection, gofumpt formatting, cross-GOOS linting to Magefile
• Fixed 404 lint issues across 86+ files (doc comments, misspell, unparam, bodyclose, nilerr, gosec permissions, goconst, prealloc, noctx context propagation, wastedassign, exhaustive, dupl)
• Added README badges (CI, Release, Go Report Card, Go Reference)

Files Changed

141 files changed, 1499 insertions(+), 830 deletions(-)

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 57.00165% with 261 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.82%. Comparing base (e4b7578) to head (e8c1e38).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
cli/src/internal/healthcheck/monitor.go	25.00%	21 Missing ⚠️
cli/src/internal/azure/standalone_logs.go	4.76%	20 Missing ⚠️
cli/src/cmd/app/commands/generate.go	46.87%	17 Missing ⚠️
cli/src/cmd/app/commands/logs.go	41.37%	15 Missing and 2 partials ⚠️
cli/src/internal/installer/installer.go	29.41%	12 Missing ⚠️
cli/src/internal/testing/orchestrator.go	64.51%	11 Missing ⚠️
cli/src/internal/dashboard/azure_logs_health.go	47.05%	9 Missing ⚠️
cli/src/internal/docker/exec.go	10.00%	9 Missing ⚠️
cli/src/internal/dashboard/azure_logs_tables.go	0.00%	8 Missing ⚠️
cli/src/internal/service/detector_frameworks.go	69.23%	8 Missing ⚠️
... and 50 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #162      +/-   ##
==========================================
- Coverage   54.86%   54.82%   -0.05%     
==========================================
  Files         147      147              
  Lines       22283    22328      +45     
==========================================
+ Hits        12226    12241      +15     
- Misses       9286     9312      +26     
- Partials      771      775       +4     

Flag	Coverage Δ
unittests	54.82% <57.00%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
cli/src/cmd/app/commands/add.go	33.63% <100.00%> (+0.60%)	⬆️
cli/src/cmd/app/commands/deps.go	41.80% <ø> (ø)
cli/src/cmd/app/commands/info.go	75.82% <100.00%> (ø)
cli/src/internal/azure/bicep.go	98.66% <100.00%> (ø)
cli/src/internal/azure/diagnostic_engine.go	70.58% <ø> (ø)
cli/src/internal/azure/diagnostics.go	24.15% <ø> (ø)
cli/src/internal/azure/discovery.go	33.68% <100.00%> (ø)
cli/src/internal/azure/loganalytics.go	30.63% <100.00%> (ø)
cli/src/internal/azure/realtime.go	69.20% <ø> (-0.64%)	⬇️
cli/src/internal/azure/validator_appservice.go	70.87% <100.00%> (ø)
... and 78 more

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