docs(readme): add Discord and WeChat community badges

[Zachary-wW]

Change Summary

• Added Discord and WeChat community badges to the header badge row of both README.md and README_zh.md (after Stars / Docker / PRs-welcome):
  • Discord links to the permanent invite of the LoongForge Community server; WeChat links to the community entry in issue Contact Us #80 (group QR + other channels).
  • shields.io badges with brand colors (#5865F2 / #07C160) and built-in logos; labels in English for consistency with the existing badge row; alt text localized. Ordering is audience-tuned: English README shows Discord first, Chinese README shows WeChat first.
• Removed the License badge from the header. Apache-2.0 remains visible in the GitHub repo sidebar and in the License section at the bottom of both READMEs, so no information is lost; the header rows also stay cleaner (ColossalAI and FastAPI similarly omit a license badge in the header).
• Docs-only change; no source code touched.

Validation

• I ran the relevant local checks.
• I added or updated tests where appropriate. (N/A — docs-only change)
• I checked compatibility with existing APIs and configurations. (N/A — docs-only change)

Verified locally:

• Discord invite resolves to the live "LoongForge Community" server (checked page metadata).
• Both shields.io badge URLs render correctly (HTTP 200, logos present).
• Rendered both READMEs and confirmed each badge row stays on a single line.

CI, GPU, and Image Impact

• This change affects dependencies, Dockerfiles, patches, or runtime environments.
• GPU validation is required. Suggested suite: llm_vlm / embodied.
• A local candidate image should be built during GPU validation.
• No GPU or image validation is required.

Reviewer Notes

• Markdown-only change; Ruff / license-header / build checks are unaffected (no .py/.sh/.cu/.cpp/.h files changed).
• Known limitation: the WeChat group QR inside issue Contact Us #80 rotates roughly weekly. The badge intentionally links to the issue (a stable entry point) rather than the image itself, but the QR in that issue needs periodic updates for the link to stay useful.
• The Slack invite currently also listed in issue Contact Us #80 is intentionally left untouched by this PR.