fix(deps): bump @contentstack/core to ^1.5.3, release 5.6.1

[cs-raj]

Problem

@contentstack/delivery-sdk 5.6.0 resolves @contentstack/core 1.5.2, whose dependency tree carries a known security vulnerability in qs (fixed in qs 6.16.0). The follow-redirects override and the TypeScript toolchain were also behind their current patch releases.

Fix

• Bump @contentstack/core to ^1.5.3 (lockfile 1.5.3), which moves qs to 6.16.0 — the qs and @contentstack/core advisories no longer appear in npm audit; the remaining advisories are all in the jest dev toolchain and were already present.
• Raise the follow-redirects override to ^1.16.1 (lockfile 1.16.1).
• Update typescript to ~5.9.3 (dev dependency; build and declaration output unchanged).
• Transitive lockfile refresh pulled in by the above: handlebars 4.7.10, acorn 8.19.0, @types/node 26.6.4, @types/ws 8.18.2, browserslist/caniuse data.
• Version 5.6.1 with the CHANGELOG entry.

Verification

Node 23 / npm 10.9: npm ci, npm run build (rollup + types) and npm run test:unit (36 suites, 720 tests) all pass. npm audit --package-lock-only drops from 40 to 38 advisories, the two removed being qs and @contentstack/core.

[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.

[github-actions]

🔒 Security Scan Results

ℹ️ Note: Only vulnerabilities with available fixes (upgrades or patches) are counted toward thresholds.

Check Type	Count (with fixes)	Without fixes	Threshold	Result
🔴 Critical Severity	0	0	10	✅ Passed
🟠 High Severity	0	0	25	✅ Passed
🟡 Medium Severity	0	0	500	✅ Passed
🔵 Low Severity	0	0	1000	✅ Passed

⏱️ SLA Breach Summary

✅ No SLA breaches detected. All vulnerabilities are within acceptable time thresholds.

Severity	Breaches (with fixes)	Breaches (no fixes)	SLA Threshold (with/no fixes)	Status
🔴 Critical	0	0	15 / 30 days	✅ Passed
🟠 High	0	0	30 / 120 days	✅ Passed
🟡 Medium	0	0	90 / 365 days	✅ Passed
🔵 Low	0	0	180 / 365 days	✅ Passed

✅ BUILD PASSED - All security checks passed

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	98.9%	993/1004
🟢	Branches	96.52%	305/316
🟢	Functions	97.79%	221/226
🟢	Lines	99.37%	945/951

Test suite run success

720 tests passing in 36 suites.

Report generated by 🧪jest coverage report action from 50ca418