refactor: apply CLAUDE.md code quality improvements and add packaging

- Add #![forbid(unsafe_code)] to main.rs (issue #3)
- Replace raw ANSI escape codes with owo-colors crate (issue #2)
- Replace manual HOME path construction with dirs::home_dir() (issue #5)
- Ship umutray.service as a static file; service::install() substitutes
  the binary path at install time instead of generating the unit at runtime
- Add packaging/PKGBUILD following Arch Rust package guidelines
- Add CLAUDE.md tracking refactor tasks
- setup.rs: clean up downloaded temp files on abort/back, save launcher
  to config only after successful install, auto-start download when a
  preset has an installer_url
- util.rs: add pick_folder() using zenity/kdialog subprocesses (no rfd)
- config.rs: populate installer_url for all 6 built-in presets with
  official download URLs
- Document the Option<Option<Vec<String>>> gamescope pattern at main.rs:307

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/detect.rs

@@ -1,5 +1,6 @@
 use crate::config::Config;
 use anyhow::Result;
+use owo_colors::OwoColorize;
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 
@@ -135,7 +136,7 @@ fn print_findings(config: &Config, by_launcher: &HashMap<String, Vec<PathBuf>>)
                 println!("  · {:12} not found", l.name);
             }
             Some(matches) if matches.len() > 1 => {
-                println!("  \x1b[33m⚠\x1b[0m {:12} multiple prefixes:", l.name);
+                println!("  {} {:12} multiple prefixes:", "⚠".yellow(), l.name);
                 for p in matches {
                     println!("                 {}", p.display());
                 }
@@ -143,11 +144,12 @@ fn print_findings(config: &Config, by_launcher: &HashMap<String, Vec<PathBuf>>)
             Some(matches) => {
                 let detected = &matches[0];
                 if *detected == l.prefix_dir {
-                    println!("  \x1b[1;32m✓\x1b[0m {:12} {}", l.name, detected.display());
+                    println!("  {} {:12} {}", "✓".green().bold(), l.name, detected.display());
                 } else {
                     any_divergent = true;
                     println!(
-                        "  \x1b[36m→\x1b[0m {:12} {}  (was {})",
+                        "  {} {:12} {}  (was {})",
+                        "→".cyan(),
                         l.name,
                         detected.display(),
                         l.prefix_dir.display()
@@ -171,19 +173,17 @@ fn apply_findings(config: &Config, by_launcher: &HashMap<String, Vec<PathBuf>>)
         };
         if matches.len() > 1 {
             ambiguous += 1;
-            println!(
-                "  \x1b[33m⚠\x1b[0m {:12} ambiguous — update via `config edit`",
-                l.name
-            );
+            println!("  {} {:12} ambiguous — update via `config edit`", "⚠".yellow(), l.name);
             continue;
         }
         let detected = &matches[0];
         if *detected == l.prefix_dir {
-            println!("  \x1b[1;32m✓\x1b[0m {:12} unchanged", l.name);
+            println!("  {} {:12} unchanged", "✓".green().bold(), l.name);
             continue;
         }
         println!(
-            "  \x1b[1;32m→\x1b[0m {:12} {} → {}",
+            "  {} {:12} {} → {}",
+            "→".green().bold(),
             l.name,
             l.prefix_dir.display(),
             detected.display()