Enhancement: Dynamic Attribute Selection Modal for Product Lines

## Summary
Enhance the product selection flow in transactional modules (Quotation, Invoice, Bill, etc.) to support dynamic product attribute selection through a modal interface.

Currently, attributes such as **Radio**, **Select**, and **Color** can be created for products. However, these attributes are not interactively selectable when adding products to transactional documents.

This enhancement introduces a **modal-based attribute selector** that appears when a product with attributes is selected from the dropdown.

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## Problem Statement
When a product has attributes defined (Radio, Select, Color), users cannot configure those attributes while adding the product to documents such as:

- Quotations
- Invoices
- Bills
- Other product line based modules

This limits product customization and creates manual workarounds.

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## Proposed Solution

### 1. Product Dropdown Behavior
When adding a **Product Line** in:
- Quotation
- Invoice
- Bill
- Any other module using product selection

The **product dropdown** should:

- Display the **Product Name**
- Allow selection as usual

### 2. Attribute Detection
After selecting a product:

- System checks if the product has **configured attributes**
- If attributes exist → **Open Attribute Selection Modal**

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## 3. Attribute Selection Modal

A **modal window** should open displaying the product attributes based on the attribute type defined during creation.

### Attribute Type Rendering

| Attribute Type | UI Behavior |
|----------------|------------|
| Radio | Show options as **radio buttons** |
| Select | Show options in a **dropdown select field** |
| Color | Show options as **color selection swatches** |

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## 4. Confirmation Action

Modal buttons:

- **Confirm / Apply**
- **Cancel**

After clicking **Confirm**:

- Selected attribute values are attached to the product line
- The product is added to the document with selected attributes

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## 5. Expected Behavior

1. User opens **Quotation / Invoice / Bill**
2. Adds **Product Line**
3. Product dropdown appears
4. User selects a product
5. If product has attributes:
- Attribute modal opens
6. User selects attribute values
7. Product line is added with selected attributes

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### Screenshots:

Start by tracing product-line selection entry points in the Quotation, Invoice, Bill, and other transactional modules. Check how product attributes of type Radio, Select, and Color are currently represented, then verify that selecting a configured product opens a modal and that Confirm attaches the chosen values while Cancel leaves the line unchanged.

Written by the indexing model from the issue text.