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>

db/schema.rb

@@ -1183,14 +1183,14 @@ ActiveRecord::Schema[7.2].define(version: 2026_01_15_100001) do
     t.datetime "updated_at", null: false
     t.string "currency"
     t.jsonb "locked_attributes", default: {}
-    t.uuid "category_id"
     t.decimal "realized_gain", precision: 19, scale: 4
     t.decimal "cost_basis_amount", precision: 19, scale: 4
     t.string "cost_basis_currency"
     t.integer "holding_period_days"
     t.string "realized_gain_confidence"
     t.string "realized_gain_currency"
-    t.index ["category_id"], name: "index_trades_on_category_id"
+    t.string "investment_activity_label"
+    t.index ["investment_activity_label"], name: "index_trades_on_investment_activity_label"
     t.index ["realized_gain"], name: "index_trades_on_realized_gain_not_null", where: "(realized_gain IS NOT NULL)"
     t.index ["security_id"], name: "index_trades_on_security_id"
   end
@@ -1348,7 +1348,6 @@ ActiveRecord::Schema[7.2].define(version: 2026_01_15_100001) do
   add_foreign_key "taggings", "tags"
   add_foreign_key "tags", "families"
   add_foreign_key "tool_calls", "messages"
-  add_foreign_key "trades", "categories"
   add_foreign_key "trades", "securities"
   add_foreign_key "transactions", "categories", on_delete: :nullify
   add_foreign_key "transactions", "merchants"