docs: add H2 database connection documentation for test data

Added README.md with instructions for connecting to the devkit H2 database,
including connection details and usage examples. Updated devkit database file.

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

Co-Authored-By: Claude <[email protected]>

Author: Mateusz Czeladka

testData/README.md

@@ -0,0 +1,24 @@
+# H2 Database Connection
+
+## Connecting to Local H2 Database
+
+To connect to the local H2 database using the H2 Shell:
+
+```bash
+java -cp h2-2.2.224.jar org.h2.tools.Shell
+```
+
+When prompted, enter the following connection details:
+
+```
+URL:      jdbc:h2:./devkit.db
+Driver:   [Enter] (org.h2.Driver - default)
+User:     rosetta_db_admin
+Password: weakpwd#123
+```
+
+Once connected, you can run SQL commands such as:
+
+```sql
+show tables;
+```