feat(01-02): add Peewee models, database init, and driver storage

- imptune/db/database.py: deferred SqliteDatabase with WAL + foreign_keys pragmas and init_db()
- imptune/db/models.py: full schema (Client, Driver, Printer, Icon) for phases 1-5
- imptune/storage/driver_store.py: SHA256 content-addressed DriverStore with dedup
- tests/test_db.py: 7 TDD tests covering all db and storage behaviors

imptune/db/database.py

@@ -0,0 +1,29 @@
+"""Peewee SQLite database instance and initialization."""
+from peewee import SqliteDatabase
+
+from imptune.config import DB_PATH
+
+# Deferred init — path is set at runtime via init_db() so tests can override DB_PATH
+db = SqliteDatabase(None)
+
+
+def init_db() -> None:
+    """Initialize the SQLite database with WAL mode and foreign keys.
+
+    Idempotent — safe to call on every application startup.
+    Creates all ORM tables if they do not already exist.
+    """
+    from imptune.db.models import Client, Driver, Printer, Icon
+
+    # Re-read DB_PATH each time so tests can patch imptune.config.DB_PATH
+    import imptune.config as cfg
+
+    db.init(
+        cfg.DB_PATH,
+        pragmas={
+            "journal_mode": "wal",
+            "foreign_keys": 1,
+        },
+    )
+    db.connect(reuse_if_open=True)
+    db.create_tables([Client, Driver, Printer, Icon], safe=True)