feat: add customer multiple addresses management

- Add CustomerAddressService with CRUD operations
- Add shop API endpoints for address management (GET, POST, PUT, DELETE)
- Add set default endpoint for address type
- Implement addresses.html with full UI (cards, modals, Alpine.js)
- Integrate saved addresses in checkout flow
  - Address selector dropdowns for shipping/billing
  - Auto-select default addresses
  - Save new address checkbox option
- Add country_iso field alongside country_name
- Add address exceptions (NotFound, LimitExceeded, InvalidType)
- Max 10 addresses per customer limit
- One default address per type (shipping/billing)
- Add unit tests for CustomerAddressService
- Add integration tests for shop addresses API

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

alembic/versions/r6f7a8b9c0d1_add_country_iso_to_addresses.py

@@ -0,0 +1,141 @@
+"""Add country_iso to customer_addresses
+
+Revision ID: r6f7a8b9c0d1
+Revises: q5e6f7a8b9c0
+Create Date: 2026-01-02
+
+Adds country_iso field to customer_addresses table and renames
+country to country_name for clarity.
+
+This migration is idempotent - it checks for existing columns before
+making changes.
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "r6f7a8b9c0d1"
+down_revision = "q5e6f7a8b9c0"
+branch_labels = None
+depends_on = None
+
+
+# Country name to ISO code mapping for backfill
+COUNTRY_ISO_MAP = {
+    "Luxembourg": "LU",
+    "Germany": "DE",
+    "France": "FR",
+    "Belgium": "BE",
+    "Netherlands": "NL",
+    "Austria": "AT",
+    "Italy": "IT",
+    "Spain": "ES",
+    "Portugal": "PT",
+    "Poland": "PL",
+    "Czech Republic": "CZ",
+    "Czechia": "CZ",
+    "Slovakia": "SK",
+    "Hungary": "HU",
+    "Romania": "RO",
+    "Bulgaria": "BG",
+    "Greece": "GR",
+    "Croatia": "HR",
+    "Slovenia": "SI",
+    "Estonia": "EE",
+    "Latvia": "LV",
+    "Lithuania": "LT",
+    "Finland": "FI",
+    "Sweden": "SE",
+    "Denmark": "DK",
+    "Ireland": "IE",
+    "Cyprus": "CY",
+    "Malta": "MT",
+    "United Kingdom": "GB",
+    "Switzerland": "CH",
+    "United States": "US",
+}
+
+
+def get_column_names(connection, table_name):
+    """Get list of column names for a table."""
+    result = connection.execute(sa.text(f"PRAGMA table_info({table_name})"))
+    return [row[1] for row in result]
+
+
+def upgrade() -> None:
+    connection = op.get_bind()
+    columns = get_column_names(connection, "customer_addresses")
+
+    # Check if we need to do anything (idempotent check)
+    has_country = "country" in columns
+    has_country_name = "country_name" in columns
+    has_country_iso = "country_iso" in columns
+
+    # If already has new columns, nothing to do
+    if has_country_name and has_country_iso:
+        print("  Columns country_name and country_iso already exist, skipping")
+        return
+
+    # If has old 'country' column, rename it and add country_iso
+    if has_country and not has_country_name:
+        with op.batch_alter_table("customer_addresses") as batch_op:
+            batch_op.alter_column(
+                "country",
+                new_column_name="country_name",
+            )
+
+    # Add country_iso if it doesn't exist
+    if not has_country_iso:
+        with op.batch_alter_table("customer_addresses") as batch_op:
+            batch_op.add_column(
+                sa.Column("country_iso", sa.String(5), nullable=True)
+            )
+
+        # Backfill country_iso from country_name
+        for country_name, iso_code in COUNTRY_ISO_MAP.items():
+            connection.execute(
+                sa.text(
+                    "UPDATE customer_addresses SET country_iso = :iso "
+                    "WHERE country_name = :name"
+                ),
+                {"iso": iso_code, "name": country_name},
+            )
+
+        # Set default for any remaining NULL values
+        connection.execute(
+            sa.text(
+                "UPDATE customer_addresses SET country_iso = 'LU' "
+                "WHERE country_iso IS NULL"
+            )
+        )
+
+        # Make country_iso NOT NULL using batch operation
+        with op.batch_alter_table("customer_addresses") as batch_op:
+            batch_op.alter_column(
+                "country_iso",
+                existing_type=sa.String(5),
+                nullable=False,
+            )
+
+
+def downgrade() -> None:
+    connection = op.get_bind()
+    columns = get_column_names(connection, "customer_addresses")
+
+    has_country_name = "country_name" in columns
+    has_country_iso = "country_iso" in columns
+    has_country = "country" in columns
+
+    # Only downgrade if in the new state
+    if has_country_name and not has_country:
+        with op.batch_alter_table("customer_addresses") as batch_op:
+            batch_op.alter_column(
+                "country_name",
+                new_column_name="country",
+            )
+
+    if has_country_iso:
+        with op.batch_alter_table("customer_addresses") as batch_op:
+            batch_op.drop_column("country_iso")