feat(build): Improve error messages for nonexistent projects/orgs

When build upload fails due to nonexistent project or organization,
now provides clearer error messages with specific guidance:

- Shows "Project not found" with guidance to check --project and --org flags
- Shows "Organization not found" with guidance to check --org flag
- Preserves original error messages for other error types

Resolves EME-175: Missing error message on build upload with nonexistent project

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

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

Author: 2 people

src/commands/build/upload.rs

@@ -325,7 +325,21 @@ pub fn execute(matches: &ArgMatches) -> Result<()> {
             }
         );
         for (path, reason) in errored_paths_and_reasons {
-            warn!("  - {} ({})", path.display(), reason);
+            let reason_str = reason.to_string();
+            // Check if this is a specific API error we can provide better messaging for
+            if reason_str.contains("Project not found") {
+                warn!("  - {}", path.display());
+                warn!("    Project not found. Ensure that you configured the correct project and organization.");
+                warn!("    Use --project and --org flags to specify the correct values.");
+            } else if reason_str.contains("organization not found")
+                || reason_str.contains("Organization not found")
+            {
+                warn!("  - {}", path.display());
+                warn!("    Organization not found. Ensure that you configured the correct organization.");
+                warn!("    Use --org flag to specify the correct organization.");
+            } else {
+                warn!("  - {} ({})", path.display(), reason);
+            }
         }
     }