Add safe SQL and redirect fixtures to the Echo pack

[malik111110]

Outcome

The Echo pack proves that parameterized SQL and a static redirect do not trigger its SQLi or redirect rules.

Maintainer guidance

The pack already has positive SQLi/redirect cases and a safe HTML case. Add negative cases beside them using the current test helper; avoid broad matcher changes.

Acceptance criteria

• Add a parameterized SQL snippet and assert no PF-ECHO-SQLI-001 finding.
• Add a static internal redirect snippet and assert no PF-ECHO-REDIRECT-001 finding.
• Each test checks the exact unwanted rule ID.
• Existing vulnerable fixtures continue to fire.
• go test ./internal/sast/frameworks/echo -count=1 passes.
• gofmt produces no diff.

Scope

Start with internal/sast/frameworks/echo/pack_test.go. Refs #7.