feat: enhance tracing with field attributes and warn logging across all handlers

Add repo_id, finding_id, and filter fields to tracing::instrument attributes
for better trace correlation in SigNoz. Replace all silently swallowed errors
(Err(_) => Vec::new()) with tracing::warn! logging across mod.rs, dast.rs,
graph.rs handlers. Add stage-level spans with .instrument() to pipeline
orchestrator for visibility into scan phases.

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

compliance-agent/src/pipeline/git.rs

@@ -78,10 +78,12 @@ impl GitOps {
         }
     }
 
+    #[tracing::instrument(skip_all, fields(repo_name = %repo_name))]
     pub fn clone_or_fetch(&self, git_url: &str, repo_name: &str) -> Result<PathBuf, AgentError> {
         let repo_path = self.base_path.join(repo_name);
 
         if repo_path.exists() {
+            tracing::info!("fetching updates for existing repo");
             self.fetch(&repo_path)?;
         } else {
             std::fs::create_dir_all(&repo_path)?;
@@ -92,7 +94,9 @@ impl GitOps {
         Ok(repo_path)
     }
 
+    #[tracing::instrument(skip_all)]
     fn clone_repo(&self, git_url: &str, repo_path: &Path) -> Result<(), AgentError> {
+        tracing::info!("cloning repo from {}", git_url);
         let mut builder = git2::build::RepoBuilder::new();
         let fetch_opts = self.credentials.fetch_options();
         builder.fetch_options(fetch_opts);