Upgrade to .NET 10.0 and enhance project maintainability (#1201)

## What changed

### .NET upgrade

All demo projects and configuration were updated to target .NET 10.0 (project files and appsettings.json dotNetVersion).
Package references were bumped to matching 10.0.0 versions.

### Asset and startup enhancements

Enabled HTML asset placeholders and cache-busting placeholders for JS assets.
Added resource preloading and import map support (ResourcePreloader / ImportMap) to App.razor and index.html to improve load performance and module resolution.
Switched asset references across CSS/JS and markup to use a centralized @assets syntax for dynamic asset path management.

### Reconnect / resilience features

Added a new ReconnectModal component (ReconnectModal.razor, + CSS and JS) and wired it into App.razor to handle connectivity/reconnect scenarios.
Program.cs updated to use app.MapStaticAssets() and app.MapRazorComponents for interactive server rendering and custom status-code handling.
Added BlazorDisableThrowNavigationException property in the server project.

### Project cleanup and refactor

Removed an unused <Folder> entry in the RCL project.
Refactored link/script tags in multiple files to use @assets for consistent, maintainable asset referencing.

### Decommissioning Hosted & WebAssembly apps

Removed the Blazor Hosted Server and WebAssembly projects and their related files: launch settings, appsettings, Razor pages (_Host.cshtml, Error.cshtml), controllers, images, sitemap, and other project-specific artifacts.
Updated the solution file to reflect those removals.

### Why it matters

Moves the codebase to the latest .NET runtime (10.0) and aligns package versions.
Improves front-end loading performance and modularity (preloading, import maps, centralized asset handling).
Adds UX resilience for connectivity issues via the reconnect modal and server-side interactive component mapping.
Cleans up dead projects/files, reducing maintenance burden.

Author: gvreddy04