feat: add basic diagnostic support for TODO comments

crates/djls-server/src/diagnostics.rs

@@ -0,0 +1,28 @@
+use tower_lsp::lsp_types::*;
+use crate::documents::TextDocument;
+
+pub struct Diagnostics;
+
+impl Diagnostics {
+    pub fn generate_for_document(document: &TextDocument) -> Vec<Diagnostic> {
+        let mut diagnostics = Vec::new();
+        
+        // TODO: Add actual diagnostic logic here
+        // For now, let's just add a placeholder diagnostic
+        if document.get_text().contains("TODO") {
+            diagnostics.push(Diagnostic {
+                range: Range {
+                    start: Position { line: 0, character: 0 },
+                    end: Position { line: 0, character: 5 },
+                },
+                severity: Some(DiagnosticSeverity::INFORMATION),
+                code: Some(NumberOrString::String("django.todo".to_string())),
+                source: Some("Django LSP".to_string()),
+                message: "Found TODO comment".to_string(),
+                ..Default::default()
+            });
+        }
+
+        diagnostics
+    }
+}