chore(web): refresh WeChat group QR (valid through 2026-08-10)

[serenakeyitan]

Closes #2147

What

Replaces packages/web/public/community/wechat-qr.png with the group owner's re-exported QR (same group, First Tree 精神股东). The previous QR expired July 28.

Same treatment as #1934: cropped to the QR square, white quiet zone, 900×900 — and encoded as a true PNG this time from the start (file(1) verified; the July refresh initially shipped JPEG bytes behind the .png name and got caught in review).

No code changes — the onboarding finale and top-bar support menu both read this one file.

Note for release

cloud.first-tree.ai picks this up at the next release tag; the live site is serving an expired code until then. New QR expires 2026-08-10; the stop-the-treadmill follow-up (updatable URL or non-expiring personal QR) is tracked in #2147.

🤖 Generated with Claude Code

[github-actions]

All contributors are covered by the First Tree CLA.
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[baixiaohang]

Recommendation: approve

• Rationale: The refreshed asset is a genuine 900×900 RGB PNG with a visible quiet zone, and the change preserves the existing single shared reference without expanding scope.

Risk level: C

• Path baseline: only packages/web/** is changed -> C
• Semantic lift: none

PR summary

• Author / repo: serenakeyitan / agent-team-foundation/first-tree
• Problem: New users and existing members currently receive an expired WeChat group QR from both the onboarding finale and the top-bar Support menu, so attempts to join the community fail silently.
• Approach: Replace the shared QR asset with the group owner's refreshed export so both user-facing surfaces pick it up at the next release, while tracking a durable non-expiring solution separately in #2147.
• Impacted modules: Web public community asset; onboarding finale and top-bar Support menu through the shared WECHAT_QR_SRC reference.

Review findings
✅ 1. The replacement is a genuine 900×900 RGB PNG with a visible white quiet zone, matching the existing .png URL and correcting the format failure caught during the previous refresh. [R4 / packages/web/public/community/wechat-qr.png]

✅ 2. Both user-facing surfaces still consume the asset through the single WECHAT_QR_SRC reference, so the refresh does not introduce a parallel or divergent QR path. [R1 / packages/web/src/lib/community.ts:15]

Action taken

• Approved exact head 15ebbae6e053447e09e6da3acc5f8ae42e2db8c8.

[yuezengwu]

Review summary

This PR refreshes the shared WeChat community QR used by the onboarding finale and top-bar Support menu. The implementation is intentionally limited to replacing packages/web/public/community/wechat-qr.png; both surfaces continue to consume it through the existing WECHAT_QR_SRC reference.

No blocking findings.

• Verified exact head 15ebbae6e053447e09e6da3acc5f8ae42e2db8c8 changes only the one binary asset.
• Verified the replacement is a genuine, non-interlaced 900×900 8-bit RGB PNG and visually retains a white quiet zone.
• Verified the existing shared reference still feeds both affected surfaces, with no duplicate or divergent asset path introduced.

Approved without waiting for CI, per review policy. The contributor still needs to satisfy the separate CLA check before merge.

[serenakeyitan]

I have read the CLA Document and I hereby sign the CLA