docs: add wiki/SharX-Overview.md

[devin-ai-integration]

Summary

Adds a new wiki/ folder at the repository root containing SharX-Overview.md, the top-level wiki page mirrored from the Devin-generated wiki ("SharX Overview" page).

The page documents:

• System Architecture (Hub-and-Spoke Panel + Worker Nodes) with a mermaid component-interaction diagram
• Key Components (Panel, Worker Nodes, Subscription System)
• Navigation Map mapping UI features to code entities and GORM data models (mermaid diagram)
• Technical Specifications table (Go 1.26, Gin, GORM/PostgreSQL, Xray-core, Next.js, sessions/JWT)
• Wiki Structure index

All "Relevant source files" and inline Sources: references point to existing files in the repo via relative links (e.g. ../README_EN.md, ../web/web.go, ../database/model/model.go).

No code changes — documentation only.

Review & Testing Checklist for Human

• Open wiki/SharX-Overview.md on GitHub and confirm both mermaid diagrams render correctly
• Spot-check a few of the relative source-file links (e.g. ../README_EN.md, ../go.mod, ../web/web.go) and confirm they resolve
• Confirm the section headings match what you expected from the Devin wiki page (System Architecture, Key Components, Navigation Map, Technical Specifications, Wiki Structure)

Notes

The mermaid node IDs from the original wiki used [bracketed labels], which is not valid Mermaid syntax for node IDs. They were rewritten to use valid node IDs with quoted labels (e.g. web_web_go["web/web.go"]) so the diagrams actually render on GitHub. The visual structure and edges/relationships are preserved.

Link to Devin session: https://app.devin.ai/sessions/ee1a52ce60d24502a1f9c1ded4fccf2f
Requested by: @konstpic

[devin-ai-integration]

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