Research: Document Context="Item" requirement for Web Forms compatibility

After extensive research and testing, I've determined that Blazor's Context
attribute is a special compile-time directive that cannot have its default
value changed from "context" to "Item" at the component definition level.

Key findings:
- Adding [Parameter] public string Context breaks Blazor's Razor compiler
- Context is NOT a regular parameter - it's a special directive
- Microsoft's own components (like Virtualize) also use default "context"
- The only solution is to document that users should use Context="Item"

Updated documentation to clarify Web Forms compatibility requirement.

Co-authored-by: csharpfritz <78577+csharpfritz@users.noreply.github.com>

Author: Copilot

docs/DataControls/DataList.md

@@ -28,7 +28,7 @@ The DataList component is meant to emulate the asp:DataList control in markup an
     - `EnableViewState`
 - `ID` should be converted to `@ref` if the component is referenced in code
 - `ItemType` MUST be defined as an attribute
-- `Context` should be used to define the object used in templates.  If not defined, the default `<INSERT>` will be available.
+- **For Web Forms compatibility, use `Context="Item"`** to access the current data item in templates with the name `@Item` instead of Blazor's default `@context`
 
 ## Web Forms Declarative Syntax