Fix: Linux Wayland/NVIDIA compatibility and Rust warnings

[digi4care]

Problem

1. Running bun run tauri dev fails with error: cargo run could not determine which binary to run
2. On Linux with Wayland and NVIDIA GPU, app fails with: Failed to create GBM buffer of size 800x600
3. Rust compiler warnings for snake_case and dead_code

Approach

1. Added default-run = "opcode" to Cargo.toml to specify the default binary
2. Added automatic detection and workaround for Wayland sessions in main.rs:
   • Detects Wayland via WAYLAND_DISPLAY or XDG_SESSION_TYPE
   • Only applies WEBKIT_DISABLE_DMABUF_RENDERER=1 when needed
   • Respects user-defined environment variables
3. Fixed snake_case warnings: renamed sessionId to session_id in web_server.rs
4. Added #[allow(dead_code)] for register_sidecar_process (kept for future use)

Limitations

• The Wayland/NVIDIA fix is a workaround for an upstream WebKitGTK issue, not a native fix
• Only affects Linux Wayland users; X11 users are unaffected

Testing

• Tested on Arch Linux with KDE 6 (Wayland) and NVIDIA GPU
• Verified bun run tauri dev runs without errors
• Verified cargo build completes without warnings