feat: Add Linux compatibility and build instructions

[ManoloZocco]

This commit introduces several changes to make Fit-Launcher fully compatible with Debian/Ubuntu-based Linux distributions. It resolves cross-platform path issues, adds a dependency installation script for Linux, and updates the documentation.

[door123456789]

I have tested your modifications on a VM with Debian 13 xfce on it and i got this error message :

"error: failed to run custom build command for fit-launcher v0.0.1 (/home/user/Fit-Launcher/src-tauri)

Caused by:
process didn't exit successfully: /home/user/Fit-Launcher/src-tauri/target/debug/build/fit-launcher-109374b090972616/build-script-build (exit status: 101)
--- stdout
Attempting to kill existing aria2c.exe processes...
Graceful termination failed, trying forceful method
Failed to execute taskkill: No such file or directory (os error 2)
cargo:rerun-if-changed=.
cargo:rerun-if-changed=local-crates/fit-launcher-aria2
cargo:rerun-if-changed=local-crates/fit-launcher-config
cargo:rerun-if-changed=local-crates/fit-launcher-ddl
cargo:rerun-if-changed=local-crates/fit-launcher-library
cargo:rerun-if-changed=local-crates/fit-launcher-scraping
cargo:rerun-if-changed=local-crates/fit-launcher-torrent
cargo:rerun-if-changed=local-crates/fit-launcher-ui-automation
cargo:rerun-if-env-changed=TAURI_CONFIG
cargo:rustc-check-cfg=cfg(desktop)
cargo:rustc-cfg=desktop
cargo:rustc-check-cfg=cfg(mobile)
cargo:rerun-if-changed=/home/user/Fit-Launcher/src-tauri/tauri.conf.json
cargo:rustc-env=TAURI_ANDROID_PACKAGE_NAME_APP_NAME=carrotrub
cargo:rustc-env=TAURI_ANDROID_PACKAGE_NAME_PREFIX=fit_launcher
cargo:rustc-check-cfg=cfg(dev)
cargo:rustc-cfg=dev
cargo:PERMISSION_FILES_PATH=/home/user/Fit-Launcher/src-tauri/target/debug/build/fit-launcher-68628dfb16ceb26b/out/app-manifest/app-permission-files
cargo:rerun-if-changed=capabilities
cargo:rerun-if-env-changed=REMOVE_UNUSED_COMMANDS
cargo:rustc-env=TAURI_ENV_TARGET_TRIPLE=x86_64-unknown-linux-gnu

--- stderr

thread 'main' panicked at build.rs:89:10:
failed to run build script: resource path binaries/aria2c-x86_64-unknown-linux-gnu doesn't exist
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish..."