Add SnapTrade brokerage integration with full trade history support (#737)

* Introduce SnapTrade integration with models, migrations, views, and activity processing logic.

* Refactor SnapTrade activities processing: improve activity fetching flow, handle pending states, and update UI elements for enhanced user feedback.

* Update Brakeman ignore file to include intentional redirect for SnapTrade OAuth portal.

* Refactor SnapTrade models, views, and processing logic: add currency extraction helper, improve pending state handling, optimize migration checks, and enhance user feedback in UI.

* Remove encryption for SnapTrade `snaptrade_user_id`, as it is an identifier, not a secret.

* Introduce `SnaptradeConnectionCleanupJob` to asynchronously handle SnapTrade connection cleanup and improve i18n for SnapTrade item status messages.

* Update SnapTrade encryption: make `snaptrade_user_secret` non-deterministic to enhance security.

---------

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

app/helpers/application_helper.rb

@@ -122,6 +122,31 @@ module ApplicationHelper
     markdown.render(text).html_safe
   end
 
+  # Formats quantity with adaptive precision based on the value size.
+  # Shows more decimal places for small quantities (common with crypto).
+  #
+  # @param qty [Numeric] The quantity to format
+  # @param max_precision [Integer] Maximum precision for very small numbers
+  # @return [String] Formatted quantity with appropriate precision
+  def format_quantity(qty)
+    return "0" if qty.nil? || qty.zero?
+
+    abs_qty = qty.abs
+
+    precision = if abs_qty >= 1
+      1     # "10.5"
+    elsif abs_qty >= 0.01
+      2     # "0.52"
+    elsif abs_qty >= 0.0001
+      4     # "0.0005"
+    else
+      8     # "0.00000052"
+    end
+
+    # Use strip_insignificant_zeros to avoid trailing zeros like "0.50000000"
+    number_with_precision(qty, precision: precision, strip_insignificant_zeros: true)
+  end
+
   private
     def calculate_total(item, money_method, negate)
       # Filter out transfer-type transactions from entries