chore(deps): security round 4 — postcss, tar

[Apexone11]

Clears 3 advisories (2 high) that landed after round 3. Lockfile-only — no manifest changes.

Alert	Package	Advisory floor	Now at
#179, #182 (high)	postcss	8.5.18	8.5.25 (all 3 lockfiles)
#180 (medium)	tar	7.5.21	7.5.22 (root + frontend)

Not included: react-router (deliberate)

The 2 remaining high alerts (#176, #177) are react-router, and the fix is 8.3.0 — a major bump from 7.18.1. CLAUDE.md lists React Router among the majors that require an explicit founder approval, so it is held out of this PR. It touches every route in the app and deserves its own PR with a full route smoke pass. Dependabot has it open as #450/#451.

Also open and awaiting the same call: #446 recharts 2→3, #447 @vitejs/plugin-react 5→6, #448 @testing-library/jest-dom 6→7, #449 rollup-plugin-visualizer 6→7 — all majors.

Validation

• Backend: lint ✅ · build ✅ · tests ✅ 3541 passed
• Frontend: lint ✅ 0 errors · build ✅ · 906 passed
• Release-log entry added (CI gate)
• playwright-smoke remains the known-red baseline (red on main since 2026-06-02)

🤖 Generated with Claude Code

Summary by Sourcery

Update dependency lockfiles to address recent security advisories for postcss and tar, and document the changes in the release log.

Enhancements:

• Record security round 4 dependency updates and remaining react-router advisories in the v2.3.0 release log entry.

Chores:

• Upgrade postcss to 8.5.25 and tar to 7.5.22 across all lockfiles to clear three new security advisories.

[cloudflare-workers-and-pages]

Deploying studyhub with    Cloudflare Pages

Latest commit:	20c56e7
Status:	✅  Deploy successful!
Preview URL:	https://8a0ee28f.studyhub-2wc.pages.dev
Branch Preview URL:	https://chore-security-round4.studyhub-2wc.pages.dev

View logs

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Lockfile-only dependency upgrades to postcss and tar across all lockfiles, plus a release-log entry documenting the security round and explicitly deferring the react-router major bump.

Flow diagram for security dependency round 4 decisions

flowchart TD
    A[Identify security advisories] --> B[Check postcss version]
    B --> C[Upgrade postcss to 8.5.25 in all lockfiles]
    A --> D[Check tar version]
    D --> E[Upgrade tar to 7.5.22 in root and frontend lockfiles]
    A --> F[Check react-router advisories]
    F --> G{Is major bump required?}
    G -->|Yes, 7→8 major| H[Defer react-router upgrade for founder sign-off]
    H --> I[Document deferral and security round in release-log.md]
    C --> I
    E --> I

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File-Level Changes

Change	Details	Files
Upgrade postcss to 8.5.25 in all lockfiles to clear high-severity advisories.	Update resolved version of postcss to 8.5.25 in the root lockfile. Update resolved version of postcss to 8.5.25 in the backend lockfile. Update resolved version of postcss to 8.5.25 in the frontend app lockfile. Adjust transitive dependency graph entries that reference the old postcss version.	package-lock.json backend/package-lock.json frontend/studyhub-app/package-lock.json
Upgrade tar to 7.5.22 in the root and frontend lockfiles to address a medium-severity advisory.	Update resolved version of tar to 7.5.22 in the root lockfile. Update resolved version of tar to 7.5.22 in the frontend app lockfile. Adjust transitive dependency graph entries that reference the old tar version.	package-lock.json frontend/studyhub-app/package-lock.json
Document security round 4 dependency updates and the deliberate exclusion of the react-router major bump in the release log.	Add a v2.3.0 release-log line summarizing the postcss and tar upgrades and the advisories they clear. Note that react-router’s remaining high alerts require a 7→8 major and are deferred pending founder sign-off.	docs/release-log.md

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[sourcery-ai]

Hey - I've reviewed your changes and they look great!

Fixed security issues:

• postcss (link)

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