feat(sqlite): initial stable release v0.9.0

Pure-Go CGO-free SQLite client with launcher lifecycle, write-mutex serialisation, health check, unit-of-work via context injection, and structured error mapping.

What's included:
- Executor / Tx / Client / Component interfaces using database/sql native types
- Tx.Commit() / Tx.Rollback() without ctx, matching the honest database/sql contract
- New(logger, cfg) constructor; database opened in OnInit
- Config struct with env-tag support; default Pragmas: WAL + 5s busy timeout + FK enforcement
- PRAGMA foreign_keys = ON enforced explicitly in OnInit
- writeMu sync.Mutex acquired by UnitOfWork.Do to serialise writes and prevent SQLITE_BUSY
- UnitOfWork via context injection; GetExecutor(ctx) returns active Tx or *sql.DB
- HandleError mapping SQLite extended error codes to xerrors codes (unique/primary-key → AlreadyExists, foreign-key → InvalidInput, ErrNoRows → NotFound)
- health.Checkable at LevelCritical; pure-Go modernc.org/sqlite driver (CGO_ENABLED=0 compatible)

Tested-via: todo-api POC integration
Reviewed-against: docs/adr/

README.md

@@ -0,0 +1,49 @@
+# sqlite
+
+Pure-Go SQLite client (`modernc.org/sqlite`, no CGO) with launcher lifecycle and health check integration.
+
+## Install
+
+```
+go get code.nochebuena.dev/go/sqlite
+```
+
+## Usage
+
+```go
+db := sqlite.New(logger, cfg)
+lc.Append(db)
+r.Get("/health", health.NewHandler(logger, db))
+```
+
+## Testing with :memory:
+
+```go
+db := sqlite.New(logger, sqlite.Config{Path: ":memory:"})
+db.OnInit()
+```
+
+## Unit of Work
+
+```go
+uow := sqlite.NewUnitOfWork(logger, db)
+
+err := uow.Do(ctx, func(ctx context.Context) error {
+    exec := db.GetExecutor(ctx) // returns the active Tx
+    _, err := exec.ExecContext(ctx, "INSERT INTO orders ...")
+    return err
+})
+```
+
+The `UnitOfWork` serialises writes via an internal mutex to prevent `SQLITE_BUSY` errors.
+
+## Configuration
+
+| Env var | Default | Description |
+|---|---|---|
+| `SQLITE_PATH` | required | File path or `:memory:` |
+| `SQLITE_MAX_OPEN_CONNS` | `1` | Max open connections |
+| `SQLITE_MAX_IDLE_CONNS` | `1` | Max idle connections |
+| `SQLITE_PRAGMAS` | `?_journal=WAL&_timeout=5000&_fk=true` | DSN pragmas |
+
+Foreign key enforcement (`PRAGMA foreign_keys = ON`) is always enabled in `OnInit`.