refactor: Tauri-to-Electron migration + monorepo restructure

[zvadaadam]

Migrates frontend from Tauri to Electron and restructures as monorepo. Frontend moves to apps/web/src/, backend to apps/backend/, sidecar to apps/sidecar/. Replaces all Tauri IPC with Electron preload bridge + HTTP/WebSocket fallbacks. Adds platform abstraction layer for clean cross-environment support. Fixes direct IPC calls to use platform/electron layer, adds capability guards for native features. Includes documentation for sidecar communication refactor (next iteration).

Key changes:

• 703 files restructured into monorepo packages
• Tauri IPC → Electron preload bridge + fallback HTTP
• Platform abstraction layer (@/platform/electron, @/platform/ws, @/platform/capabilities)
• All Electron API calls through safe wrapper with web-mode fallback
• Capability-gated native features (folder picker, auto-update)
• WebSocket query protocol for all backend commands (PTY, fs-watch, browser-server, messaging)

Known issues documented for next PR:

• 4 missing Electron IPC handlers for browser/simulator automation (separate PR)
• Sidecar communication should route through WebSocket instead of HTTP relay (architectural refactor planned)

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Electron-based desktop framework replacing Tauri for improved cross-platform stability.
  • File browser with workspace scanning, fuzzy search, and safe file preview.
  • Browser server automation with managed lifecycle and authentication.
  • WebSocket agent communication via JSON-RPC protocol.
  • Terminal (PTY) session support for interactive command execution.
  • Auto-updater integration for seamless application updates.

• Documentation

  • Updated development and release guides for new Electron architecture.

• Chores

  • Enhanced test coverage and infrastructure.
  • Improved code consistency and build configuration.