Improve investment activity labels UX and add convert-to-trade feature (#649)

* Add `investment_activity_label` to trades and enhance activity label handling

- Introduced `investment_activity_label` column to the `trades` table with a migration.
- Backfilled existing `trades` with activity labels based on quantity (`Buy`, `Sell`, or `Other`).
- Replaced `category_id` in trades with `investment_activity_label` for better alignment with transaction labels.
- Updated views and controllers to display and manage activity labels for trades.
- Added localized badge components for displaying and editing labels dynamically.
- Enhanced `PlaidAccount::Investments::TransactionsProcessor` to assign and process activity labels automatically.
- Added investment flows section to reports for tracking contributions and withdrawals.
- Refactored related tests and models for consistency and to ensure proper validation and filtering.

* Improve handling of `investment_activity_label`, trade type, and security selection in trades and transactions

- Refined label assignment logic in `trades_controller` to default to `Buy`/`Sell` based on transaction nature.
- Simplified security selection in `transactions_controller` by resolving via unique IDs or custom tickers.
- Streamlined UI for trade and transaction forms by updating dropdown options and label text.
- Enabled quick-edit badges to open `convert_to_trade` modal when applicable, enhancing flexibility.
- Adjusted tests and views to align with updated workflows and ensure consistent behavior.

* Improve handling of `investment_activity_label`, trade type, and security selection in trades and transactions

- Refined label assignment logic in `trades_controller` to default to `Buy`/`Sell` based on transaction nature.
- Simplified security selection in `transactions_controller` by resolving via unique IDs or custom tickers.
- Streamlined UI for trade and transaction forms by updating dropdown options and label text.
- Enabled quick-edit badges to open `convert_to_trade` modal when applicable, enhancing flexibility.
- Adjusted tests and views to align with updated workflows and ensure consistent behavior.

* Improve handling of `investment_activity_label`, trade type, and security selection in trades and transactions

- Refined label assignment logic in `trades_controller` to default to `Buy`/`Sell` based on transaction nature.
- Simplified security selection in `transactions_controller` by resolving via unique IDs or custom tickers.
- Streamlined UI for trade and transaction forms by updating dropdown options and label text.
- Enabled quick-edit badges to open `convert_to_trade` modal when applicable, enhancing flexibility.
- Adjusted tests and views to align with updated workflows and ensure consistent behavior.

* Add safeguard for `dropdownTarget` existence in quick edit controller

- Prevent errors by ensuring `dropdownTarget` is present before toggling its visibility.

* Fix undefined method 'category' for Trade on mobile view

Trade model uses investment_activity_label, not category. The upstream
merge introduced a call to trade.category which doesn't exist. Use the
activity label badge on mobile instead.

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

* Fix activity label logic for zero/blank quantity and sell inference

- Return `nil` for blank or zero quantity in `investment_activity_label_for`.
- Correct `is_sell` logic to use the amount’s sign properly in `transactions_controller`.

* Fix i18n key paths in transactions controller for convert_to_trade

- Update flash message translations to use full i18n paths.
- Use `BigDecimal` for quantity and price calculations to improve precision.

---------

Co-authored-by: Josh Waldrep <joshua.waldrep5+github@gmail.com>
Co-authored-by: luckyPipewrench <luckypipewrench@proton.me>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

app/models/trade_import.rb

@@ -21,7 +21,7 @@ class TradeImport < Import
           qty: row.qty,
           currency: row.currency.presence || mapped_account.currency,
           price: row.price,
-          category: investment_category_for(row.qty, mapped_account.family),
+          investment_activity_label: investment_activity_label_for(row.qty),
           entry: Entry.new(
             account: mapped_account,
             date: row.date_iso,
@@ -78,12 +78,11 @@ class TradeImport < Import
   end
 
   private
-    def investment_category_for(qty, family)
-      # Buy trades (positive qty) are categorized as "Savings & Investments"
-      # Sell trades are left uncategorized - users will be prompted to categorize
-      return nil unless qty.to_d.positive?
-
-      family.categories.find_by(name: "Savings & Investments")
+    def investment_activity_label_for(qty)
+      # Set activity label based on quantity signage
+      # Buy trades have positive qty, Sell trades have negative qty
+      return nil if qty.blank? || qty.to_d.zero?
+      qty.to_d.positive? ? "Buy" : "Sell"
     end
 
     def find_or_create_security(ticker: nil, exchange_operating_mic: nil)