Cover NestJS SSRF with vulnerable and safe fixtures

[malik111110]

Outcome

PF-NESTJS-SSRF-001 documents its source-to-sink expectation with focused positive and negative cases.

Maintainer guidance

Use the existing NestJS test helpers and keep the snippets minimal. A safe case may use a fixed upstream URL or explicit allowlist validation that the current safe-pattern model understands.

Acceptance criteria

• Add a controller case that sends request-controlled input to the HTTP client sink.
• Assert the finding ID is PF-NESTJS-SSRF-001.
• Add a constant or validated-destination safe case.
• Assert the safe case produces no PF-NESTJS-SSRF-001 finding.
• Tests use source snippets only and make no network request.
• go test ./internal/sast/frameworks/nestjs -count=1 passes.
• gofmt produces no diff.

Scope

Start with internal/sast/frameworks/nestjs/pack_test.go and internal/sast/frameworks/nestjs/rules.go. Refs #7.