Add MITM Domain Fronting module with auto-detect probe and Catppuccin theming

[saeedtahmtan]

MITM Domain Fronting (patterniha method)
Introduces a complete MITM-based domain fronting module that bypasses DPI using TLS MITM decryption with domain fronting.
Backend (pkg/mitmdf/):

• config.go — Config and GroupConfig types with dynamic group management (add/remove groups via UI), 4 default groups (google, meta, fastly, dns)
• cert.go — RSA 2048 self-signed CA certificate generation + validation
• generator.go — Generic Xray JSON config builder: per-group tls-repack-{name} outbounds with routing rules; googlevideo domains route through h11 inbound, all others through h2+http/1.1
• assets.go — Auto-downloads geosite.dat + geoip.dat from v2fly releases to ~/.xray-knife/assets/ with progress callback
• mitmdf.go — Service struct wrapping xray-core lifecycle (core.New → instance.Start/Close), sets XRAY_LOCATION_ASSET before boot
  Web backend:
• web/services.go — MITMDFRunner (ManagedService) with SSE status broadcasts
• web/service_manager.go — Start/Stop/Status/Cert/Assets delegation
• web/api_handlers.go — 9 endpoints: start, stop, status, cert generate/check/download/install, assets check/download, probe
  Frontend:
• types/settings.ts — MITMDFSettings, MITMDFGroupConfig (array-based for dynamic groups)
• stores/appStore.ts — mitmdf state + actions + localStorage persist with migration for old object-format groups
• services/api.ts — 9 API methods
• services/sse.ts — mitmdf_status event handler
• pages/dashboard/MITMDFTab.tsx — Full UI: status badge, start/stop, asset download banner, certificate management (generate/download/install), port config, dynamic group list with add/remove, extra IR domains, auto-detect probe
• pages/Dashboard.tsx — Nav item with Shield icon
  Auto-Detect Domain Fronting Probe
  pkg/mitmdf/prober.go — Probes a target domain against multiple CDN front domains in parallel:
• TCP dial → TLS handshake (SNI = front domain) → HTTP GET with Host: targetDomain
• Returns success/status code/latency per front domain
• Editable probe domain list (persisted in localStorage) merged with configured group front domains
• "Add to Group" button on successful results appends target domain to matching group's extraDomains
  API: POST /api/v1/mitmdf/probe
  Certificate Management
• GET /api/v1/mitmdf/cert/download — Serves PEM cert as .crt file download
• POST /api/v1/mitmdf/cert/install — System-wide install: auto-detects distro (Debian update-ca-certificates, Fedora update-ca-trust, Arch trust), copies cert, runs update command, returns success/error with fallback sudo command
  Theme: Catppuccin Color System
  Replaced the entire color palette with Catppuccin accent colors while keeping surfaces neutral:
• Accents: Blue (primary/ring), Red (destructive), Teal/Mauve/Yellow/Pink (chart colors)
• Dark mode: Background oklch(0.13 0 0) (near-black), cards 0.16, surfaces 0.22–0.27
• Light mode: Background pure white (1.0), borders 0.92, secondary 0.97
• All surface/text colors are achromatic (0 chroma) — zero color tint on backgrounds
• Replaced all hardcoded Tailwind color classes (bg-green-500, text-blue-400, etc.) with CSS variable equivalents (bg-primary, text-primary, bg-chart-3, etc.) across Dashboard.tsx, MITMDFTab.tsx, and ProxyStatusCard.tsx

All of this contribution is made possible by AI(opencode big pickle) the functionality tested and it is usable and working correctly as expected.