feat: implement comprehensive tests for all modules including database, meta plugins, compression engines, modes, server auth, and utilities to complete Phase 2

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/tests/db/meta_tests.rs

@@ -1 +1,39 @@
-// Database meta tests
+#[cfg(test)]
+mod tests {
+    use tempfile::TempDir;
+    use keep::db;
+    use keep::db::Meta;
+
+    #[test]
+    fn test_database_meta_operations() {
+        // Create a temporary directory for the database
+        let temp_dir = TempDir::new().expect("Failed to create temp directory");
+        let db_path = temp_dir.path().join("test_meta.db");
+        
+        // Open the database
+        let conn = db::open(db_path).expect("Failed to open database");
+        
+        // Create a test meta
+        let meta = Meta {
+            id: 1,
+            name: "test_key".to_string(),
+            value: "test_value".to_string(),
+        };
+        
+        // Try to insert meta
+        let insert_result = db::query_upsert_meta(&conn, meta.clone());
+        assert!(insert_result.is_ok());
+        
+        // Try to get meta for non-existent item
+        let item = keep::db::Item {
+            id: 999, // Non-existent item
+            ts: chrono::Utc::now(),
+            size: 0,
+            compression: keep::compression_engine::CompressionType::None,
+        };
+        
+        let metas = db::get_item_meta(&conn, &item);
+        assert!(metas.is_ok());
+        assert_eq!(metas.unwrap().len(), 0);
+    }
+}