feat!: _async() twin support for methods that actually reach the database

[robinvandernoord]

• feat(async): add asynchronous execution scaffolding
• chore(docs): reformat Python examples
• feat(async): add async query execution for SQLite and Postgres
• feat(async): implement async CRUD and query execution
• test: add tests for the remaining async stubs
• feat(async): implement remaining async query and table operations
• test(async): expand async execution parity and defect coverage
• chore(testing): configure source-only coverage
• fix(async): serialize SQLite execution and align async operations with pydal
• chore(typing): configure ty and tighten project annotations
• test: get rid of monkeypatch.setattr slop
• refactor(async-execution): extract async pool lifecycle into manager
• refactor(typescript): simplify registry world access
• docs(typedal): remove brittle upstream line references
• test(async-execution): add regression coverage for transaction and parity issues
• fix(async): preserve transaction boundaries across async and sync paths
• fix(tables): keep async model operations non-blocking and compatible
• test(fixtures): close PostgreSQL databases after each test
• fix(async): track pending writes per task
• test(async): cover transaction isolation and pool cleanup
• docs: remove stale rfc file

[robinvandernoord]

#12