Implement Remote Guide Sync, Bot Bypass, and Startup Auto-fetch

[StandardCodebase]

Overview:
Added ability to fetch remote Markdown guides from external repositories, bypassing common WAF bot-detection mechanisms. It implements an automated fetching routine on boot, patches Go 1.22 routing panics, and repairs the Docker build pipeline.

Specific Changes:

• internal/handler/handler.go:

• Updated ImportRemoteGuide: Replaced the standard http.Get call with a custom http.Client featuring a 15-second timeout and a spoofed browser User-Agent (Mozilla/5.0...). This prevents 502 Bad Gateway errors by bypassing bot blockers on platforms like Codeberg and GitHub.

• Added SyncGuideOnStartup: Introduced a new background method that automatically downloads a specified remote guide, saves it directly to the data/clearnet/remote/ directory, and clears the manifestCache so the UI updates instantly on boot.

• main.go:

• Routing Stability: Removed duplicate route declarations for /import and /static/ on the http.ServeMux. This resolves the pattern conflicts panic introduced by Go 1.22's strict routing rules.

• Startup Execution: Injected node.SyncGuideOnStartup() to automatically pull the official Git documentation on server initialization before the HTTP server starts listening.

• Dockerfile:

• Multi-Stage Build Fix: modified the Stage 1 builder (golang:1.26-alpine) to compile the Go binary directly from the source code, resolving the pull access denial when copying artifacts to the final, restricted reduser Alpine container.

[KrishnaSSH]

refactor