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/javascript/controllers/convert_to_trade_controller.js

@@ -0,0 +1,21 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static targets = ["customWrapper", "customField", "tickerSelect"]
+
+  toggleCustomTicker(event) {
+    const value = event.target.value
+
+    if (value === "__custom__") {
+      // Show custom ticker field
+      this.customWrapperTarget.classList.remove("hidden")
+      this.customFieldTarget.required = true
+      this.customFieldTarget.focus()
+    } else {
+      // Hide custom ticker field
+      this.customWrapperTarget.classList.add("hidden")
+      this.customFieldTarget.required = false
+      this.customFieldTarget.value = ""
+    }
+  }
+}