Shorten README into a PWMenu project card

[newfpv]

What changed

• Replaced the 407-line manual-style README with a 66-line project card.
• Kept the full PWMenu Wiki button at the very top.
• Added release, CI, and license badges.
• Added a compact three-screenshot product preview using existing repository assets.
• Reduced the feature description to eight high-level highlights.
• Kept only the minimal tagged installation, enablement, and service-restart commands.
• Routed detailed installation requirements, module configuration, WPA-sec, OHC, VLESS/Xray, quality, exports, map controls, cleanup, and troubleshooting to the Wiki.
• Preserved the authorized-use and sensitive-data notice plus release, changelog, issue, and license links.

Why

The README had grown into a second copy of the documentation and was difficult to scan on the repository landing page. The Wiki is the canonical detailed guide, while the README now works as a concise project introduction.

Validation

• git diff --check
• Verified all local image and document targets referenced by the README exist.
• Full test suite: 59 tests passed.