Add Coinbase exchange integration with CDP API support (#704)

* **Add Coinbase integration with item and account management**
- Creates migrations for `coinbase_items` and `coinbase_accounts`.
- Adds models, controllers, views, and background tasks to support account linking, syncing, and transaction handling.
- Implements Coinbase API client and adapter for seamless integration.
- Supports ActiveRecord encryption for secure credential storage.
- Adds UI components for provider setup, account management, and synchronization.

* Localize Coinbase-related UI strings, refine account linking for security, and add timeouts to Coinbase API requests.

* Localize Coinbase account handling to support native currencies (USD, EUR, GBP, etc.) across balances, trades, holdings, and transactions.

* Improve Coinbase processing with timezone-safe parsing, native currency support, and immediate holdings updates.

* Improve trend percentage formatting and enhance race condition handling for Coinbase account linking.

* Fix log message wording for orphan cleanup

* Ensure `selected_accounts` parameter is sanitized by rejecting blank entries.

* Add tests for Coinbase integration: account, item, and controller coverage

- Adds unit tests for `CoinbaseAccount` and `CoinbaseItem` models.
- Adds integration tests for `CoinbaseItemsController`.
- Introduces Stimulus `select-all` controller for UI checkbox handling.
- Localizes UI strings and logging for Coinbase integration.

* Update test fixtures to use consistent placeholder API keys and secrets

* Refine `coinbase_item` tests to ensure deterministic ordering and improve scope assertions.

* Integrate `SyncStats::Collector` into Coinbase syncer to streamline statistics collection and enhance consistency.

* Localize Coinbase sync status messages and improve sync summary test coverage.

* Update `CoinbaseItem` encryption: use deterministic encryption for `api_key` and standard for `api_secret`.

* fix schema drift

* Beta labels to lower expectations

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Co-authored-by: luckyPipewrench <luckypipewrench@proton.me>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

app/models/holding/materializer.rb

@@ -53,6 +53,16 @@ class Holding::Materializer
         key = holding_key(holding)
         existing = existing_holdings_map[key]
 
+        # Skip provider-sourced holdings - they have authoritative data from the provider
+        # (e.g., Coinbase, SimpleFIN) and should not be overwritten by calculated holdings
+        if existing&.account_provider_id.present?
+          Rails.logger.debug(
+            "Holding::Materializer - Skipping provider-sourced holding id=#{existing.id} " \
+            "security_id=#{existing.security_id} date=#{existing.date}"
+          )
+          next
+        end
+
         reconciled = Holding::CostBasisReconciler.reconcile(
           existing_holding: existing,
           incoming_cost_basis: holding.cost_basis,