feat: Support multiple crypto wallets with same token (#676)

* feat: Support multiple crypto wallets with same token

Allows users to import multiple wallets containing the same
cryptocurrency (e.g., ETH on different wallet addresses).

Changes:
- Add wallet_address column to coinstats_accounts
- Update uniqueness validation to include wallet_address
- Extract and store wallet address in WalletLinker
- Add composite unique index on [item_id, account_id, wallet_address]
- Add tests for multi-wallet support and backwards compatibility

Users can now have:
- ETH (0xAAA...) → "Ethereum (0xAA...AA)"
- ETH (0xBBB...) → "Ethereum (0xBB...BB)"

Backwards compatible: existing accounts with wallet_address: nil
continue to work.

* style: Fix array bracket spacing in migration

* chore: Update schema.rb with wallet_address column and index

Add the missing wallet_address column and composite unique index
to db/schema.rb for CI compatibility with db:schema:load

* test: Add test for wallet deletion with same token different addresses

Verifies that deleting one wallet does not affect other wallets
that share the same token but have different addresses.

Addresses review comment from @EthanC via @jjmata

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

test/models/coinstats_account_test.rb

@@ -199,4 +199,95 @@ class CoinstatsAccountTest < ActiveSupport::TestCase
 
     assert_equal [], @coinstats_account.raw_transactions_payload
   end
+
+  # Multi-wallet tests
+  test "account_id is unique per coinstats_item and wallet_address" do
+    @coinstats_account.update!(
+      account_id: "ethereum",
+      wallet_address: "0xAAA123"
+    )
+
+    duplicate = @coinstats_item.coinstats_accounts.build(
+      name: "Duplicate Ethereum",
+      currency: "USD",
+      account_id: "ethereum",
+      wallet_address: "0xAAA123"
+    )
+
+    assert_not duplicate.valid?
+    assert_includes duplicate.errors[:account_id], "has already been taken"
+  end
+
+  test "allows same account_id with different wallet_address" do
+    @coinstats_account.update!(
+      account_id: "ethereum",
+      wallet_address: "0xAAA123"
+    )
+
+    different_wallet = @coinstats_item.coinstats_accounts.build(
+      name: "Different Ethereum Wallet",
+      currency: "USD",
+      account_id: "ethereum",
+      wallet_address: "0xBBB456"
+    )
+
+    assert different_wallet.valid?
+  end
+
+  test "allows multiple accounts with nil wallet_address for backwards compatibility" do
+    first_account = @coinstats_item.coinstats_accounts.create!(
+      name: "Legacy Account 1",
+      currency: "USD",
+      account_id: "bitcoin",
+      wallet_address: nil
+    )
+
+    second_account = @coinstats_item.coinstats_accounts.build(
+      name: "Legacy Account 2",
+      currency: "USD",
+      account_id: "ethereum",
+      wallet_address: nil
+    )
+
+    assert second_account.valid?
+    assert second_account.save
+  end
+
+  test "deleting one wallet does not affect other wallets with same token but different address" do
+    # Create two wallets with the same token (ethereum) but different addresses
+    wallet_a = @coinstats_item.coinstats_accounts.create!(
+      name: "Ethereum Wallet A",
+      currency: "USD",
+      account_id: "ethereum",
+      wallet_address: "0xAAA111",
+      current_balance: 1000.00
+    )
+
+    wallet_b = @coinstats_item.coinstats_accounts.create!(
+      name: "Ethereum Wallet B",
+      currency: "USD",
+      account_id: "ethereum",
+      wallet_address: "0xBBB222",
+      current_balance: 2000.00
+    )
+
+    # Verify both wallets exist
+    assert_equal 3, @coinstats_item.coinstats_accounts.count # includes @coinstats_account from setup
+
+    # Delete wallet A
+    wallet_a.destroy!
+
+    # Verify only wallet A was deleted, wallet B still exists
+    @coinstats_item.reload
+    assert_equal 2, @coinstats_item.coinstats_accounts.count
+
+    # Verify wallet B is still intact with correct data
+    wallet_b.reload
+    assert_equal "Ethereum Wallet B", wallet_b.name
+    assert_equal "0xBBB222", wallet_b.wallet_address
+    assert_equal BigDecimal("2000.00"), wallet_b.current_balance
+
+    # Verify wallet A no longer exists
+    assert_nil CoinstatsAccount.find_by(id: wallet_a.id)
+  end
 end