feat: improve depot UX and packaging workflow

- add shared terminal UI helpers for colored info/warn/success logs and yes/no prompts
- add Python build backend (PEP 517/setup.py wheel build + install) and expose python in interactive spec creation
- expand spec/build flags (post_configure, make phase targets/dirs, configure_file, no_strip, no_compress_man)
- support split-output staging with internal .depot output dirs, shell helpers (haul/subdestdir), and per-output deps/provides overrides
- improve staging with ELF auto-strip and zstd manpage compression (with opt-out flags)
- enforce runtime deps before install and support legacy lifecycle hook script names
- improve manual source handling with files/urls lists and stricter validation

src/config.rs

@@ -74,7 +74,7 @@ impl Config {
         };
 
         if let Err(e) = config.load_system(&abs_rootfs) {
-            eprintln!("Warning: Failed to load system config: {}", e);
+            crate::log_warn!("Failed to load system config: {}", e);
         }
 
         config