fix(#1328): resolve RenderFlex overflow in AI dialog on Android

[AbdelrahmanELBORGY]

PR Description

Root Cause:

The primary crash was caused by a Row layout containing the "Select Model Provider" text and dropdown, which resulted in a horizontal RenderFlex overflow on mobile screens. Additionally, the main dialog Column lacked scrolling capabilities, leading to vertical overflow on shorter devices.

Fix:

• Converted the Provider selector layout from a Row to a Column to prevent the horizontal RenderFlex crash.
• Wrapped the main medium-window content in a SingleChildScrollView to allow safe vertical scrolling.
• Wrapped the ADDropdownButton in a decorated Container to provide a standard UI border, making the dropdown visually distinct.

Visual Proof:

Before (Issue #1328)	After (This PR)

Related Issues

• Closes RenderFlex overflow in AI Model Selector dialog on Android #1328

Checklist

• I have gone through the contributing guide
• I have updated my branch and synced it with project main branch before making this PR
• I am using the latest Flutter stable branch (run flutter upgrade and verify)
• I have run the tests (flutter test) and all tests are passing

Added/updated tests?

• Yes
• No, and this is why: This is purely a UI layout fix for mobile constraints, no core backend or state logic was altered.

OS on which you have developed and tested the feature?

• Windows
• macOS
• Linux

[codealchemist007]

@AbdelrahmanELBORGY I've just tested this on Android 15 (Redmi) and can confirm that the overflow is resolved. The Row→Column approach works great. Nice catch!

[praaatap]

@AbdelrahmanELBORGY check #1269

[AbdelrahmanELBORGY]

@praaatap yes I have seen that after i have submitted my PR, thanks for pointing out brother