Add schema selector to the editor toolbar for schema-aware databases
(PostgreSQL, SQL Server, Oracle). When a schema is selected, the backend
sets the appropriate search_path before executing queries so users no
longer need to write schema-qualified table names.
Introduce src-web (axum HTTP server) exposing all 43 database operations
as REST APIs with SSE streaming for AI, transfers, and SQL file execution.
Frontend adapts automatically between Tauri and HTTP backends via api.ts.
Includes password authentication, Docker packaging, and login page.
t8y2