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/models.py

@@ -0,0 +1,78 @@
+"""Peewee ORM models — full schema for phases 1-5."""
+from datetime import datetime
+
+from peewee import (
+    BooleanField,
+    CharField,
+    DateTimeField,
+    ForeignKeyField,
+    IntegerField,
+    Model,
+)
+
+from imptune.db.database import db
+
+
+class BaseModel(Model):
+    """Base model that binds all models to the shared db instance."""
+
+    class Meta:
+        database = db
+
+
+class Client(BaseModel):
+    """Represents a deployment target (AD client / OU)."""
+
+    name = CharField(unique=True)
+    created_at = DateTimeField(default=datetime.utcnow)
+
+    class Meta:
+        table_name = "client"
+
+
+class Driver(BaseModel):
+    """Uploaded printer driver package (content-addressed by SHA256)."""
+
+    sha256 = CharField(unique=True, index=True)
+    original_filename = CharField()
+    size_bytes = IntegerField()
+    uploaded_at = DateTimeField(default=datetime.utcnow)
+    driver_desc = CharField(null=True)
+    inf_filename = CharField(null=True)
+    architecture = CharField(null=True)
+    has_cat_file = BooleanField(default=False)
+
+    class Meta:
+        table_name = "driver"
+
+
+class Printer(BaseModel):
+    """Printer configuration record."""
+
+    name = CharField()
+    ip_address = CharField()
+    port_name = CharField()
+    client = ForeignKeyField(Client, null=True, backref="printers")
+    driver = ForeignKeyField(Driver, null=True, backref="printers")
+    duplex_mode = CharField(default="OneSided")
+    color_mode = BooleanField(default=True)
+    paper_size = CharField(default="A4")
+    collate = BooleanField(default=True)
+    created_at = DateTimeField(default=datetime.utcnow)
+    updated_at = DateTimeField(default=datetime.utcnow)
+
+    class Meta:
+        table_name = "printer"
+
+
+class Icon(BaseModel):
+    """Printer icon image (one per printer)."""
+
+    printer = ForeignKeyField(Printer, unique=True, backref="icons")
+    sha256 = CharField()
+    original_filename = CharField()
+    size_bytes = IntegerField()
+    uploaded_at = DateTimeField(default=datetime.utcnow)
+
+    class Meta:
+        table_name = "icon"