fix: lower log level for missing base ref detection (EME-369)

Changes the logging level from warn to info when failing to detect base
branch reference in build uploads. This reduces noise in build logs for
common scenarios including detached HEAD states in PRs and main/master
branch builds where base ref detection failures are expected.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: runningcode

src/commands/build/upload.rs

@@ -192,7 +192,7 @@ pub fn execute(matches: &ArgMatches) -> Result<()> {
                             Some(base_ref_name)
                         }
                         Err(e) => {
-                            warn!("Could not detect base branch reference: {}", e);
+                            info!("Could not detect base branch reference: {}", e);
                             None
                         }
                     })