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>

app/models/coinstats_account.rb

@@ -10,7 +10,7 @@ class CoinstatsAccount < ApplicationRecord
   has_one :account, through: :account_provider, source: :account
 
   validates :name, :currency, presence: true
-  validates :account_id, uniqueness: { scope: :coinstats_item_id, allow_nil: true }
+  validates :account_id, uniqueness: { scope: [ :coinstats_item_id, :wallet_address ], allow_nil: true }
 
   # Alias for compatibility with provider adapter pattern
   alias_method :current_account, :account

app/models/coinstats_item/wallet_linker.rb

@@ -85,7 +85,8 @@ class CoinstatsItem::WalletLinker
           name: account_name,
           currency: "USD",
           current_balance: current_balance,
-          account_id: token_id
+          account_id: token_id,
+          wallet_address: address
         )
 
         # Store wallet metadata for future syncs