Add WebAPI middleware for multi-instance Roslyn Bridge routing

Add RoslynBridge.WebApi - ASP.NET Core 8.0 middleware that:
- Provides a centralized REST API for accessing multiple VS instances
- Manages instance registry with discovery by port, solution, or PID
- Proxies requests to the appropriate VS instance
- Tracks request/response history for debugging
- Auto-cleanup of stale instances via background service

Features:
- Health endpoints: /api/health, /api/health/ping
- Roslyn endpoints: /api/roslyn/projects, /api/roslyn/diagnostics, etc.
- Instance management: /api/instances (register, heartbeat, unregister)
- History tracking: /api/history, /api/history/stats
- Swagger UI at root (/) for API documentation
- CORS enabled for web applications

Services:
- InstanceRegistryService: Thread-safe registry of VS instances
- HistoryService: In-memory request/response history (max 1000 entries)
- InstanceCleanupService: Background service to remove stale instances
- RoslynBridgeClient: HTTP client for proxying to VS instances

Update RoslynBridge.sln to include RoslynBridge.WebApi project.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

RoslynBridge.WebApi/Models/HealthCheckResponse.cs

@@ -0,0 +1,32 @@
+namespace RoslynBridge.WebApi.Models;
+
+/// <summary>
+/// Health check response for service status
+/// </summary>
+public class HealthCheckResponse
+{
+    /// <summary>
+    /// Overall health status
+    /// </summary>
+    public string Status { get; set; } = "Healthy";
+
+    /// <summary>
+    /// Web API service status
+    /// </summary>
+    public string WebApiStatus { get; set; } = "Running";
+
+    /// <summary>
+    /// Visual Studio plugin connection status
+    /// </summary>
+    public string VsPluginStatus { get; set; } = "Unknown";
+
+    /// <summary>
+    /// Timestamp of the health check
+    /// </summary>
+    public DateTime Timestamp { get; set; } = DateTime.UtcNow;
+
+    /// <summary>
+    /// API version
+    /// </summary>
+    public string Version { get; set; } = "1.0.0";
+}

RoslynBridge.WebApi/Models/QueryHistoryEntry.cs

@@ -0,0 +1,52 @@
+namespace RoslynBridge.WebApi.Models;
+
+/// <summary>
+/// Represents a single query history entry with request and response information
+/// </summary>
+public class QueryHistoryEntry
+{
+    /// <summary>
+    /// Unique identifier for this history entry
+    /// </summary>
+    public string Id { get; set; } = Guid.NewGuid().ToString();
+
+    /// <summary>
+    /// Timestamp when the request was received
+    /// </summary>
+    public DateTime Timestamp { get; set; } = DateTime.UtcNow;
+
+    /// <summary>
+    /// The endpoint path that was called
+    /// </summary>
+    public string Path { get; set; } = string.Empty;
+
+    /// <summary>
+    /// HTTP method used
+    /// </summary>
+    public string Method { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The Roslyn query request
+    /// </summary>
+    public RoslynQueryRequest? Request { get; set; }
+
+    /// <summary>
+    /// The Roslyn query response
+    /// </summary>
+    public RoslynQueryResponse? Response { get; set; }
+
+    /// <summary>
+    /// Request duration in milliseconds
+    /// </summary>
+    public long DurationMs { get; set; }
+
+    /// <summary>
+    /// Whether the request was successful
+    /// </summary>
+    public bool Success { get; set; }
+
+    /// <summary>
+    /// Client IP address
+    /// </summary>
+    public string? ClientIp { get; set; }
+}

RoslynBridge.WebApi/Models/RoslynQueryRequest.cs

@@ -0,0 +1,65 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace RoslynBridge.WebApi.Models;
+
+/// <summary>
+/// Request model for Roslyn query operations
+/// </summary>
+public class RoslynQueryRequest
+{
+    /// <summary>
+    /// Type of query to execute (e.g., "getsymbol", "getdocument", "findreferences")
+    /// </summary>
+    [Required]
+    public string QueryType { get; set; } = string.Empty;
+
+    /// <summary>
+    /// File path for file-based operations
+    /// </summary>
+    public string? FilePath { get; set; }
+
+    /// <summary>
+    /// Symbol name for symbol-based operations
+    /// </summary>
+    public string? SymbolName { get; set; }
+
+    /// <summary>
+    /// Line number (1-based) for position-based operations
+    /// </summary>
+    public int? Line { get; set; }
+
+    /// <summary>
+    /// Column number (0-based) for position-based operations
+    /// </summary>
+    public int? Column { get; set; }
+
+    /// <summary>
+    /// Additional parameters for the query
+    /// </summary>
+    public Dictionary<string, string>? Parameters { get; set; }
+
+    /// <summary>
+    /// Project name for project operations
+    /// </summary>
+    public string? ProjectName { get; set; }
+
+    /// <summary>
+    /// Package name for NuGet operations
+    /// </summary>
+    public string? PackageName { get; set; }
+
+    /// <summary>
+    /// Version for NuGet package operations
+    /// </summary>
+    public string? Version { get; set; }
+
+    /// <summary>
+    /// Build configuration (Debug/Release)
+    /// </summary>
+    public string? Configuration { get; set; }
+
+    /// <summary>
+    /// Directory path for directory operations
+    /// </summary>
+    public string? DirectoryPath { get; set; }
+}

RoslynBridge.WebApi/Models/RoslynQueryResponse.cs

@@ -0,0 +1,27 @@
+namespace RoslynBridge.WebApi.Models;
+
+/// <summary>
+/// Response model for Roslyn query operations
+/// </summary>
+public class RoslynQueryResponse
+{
+    /// <summary>
+    /// Indicates whether the operation was successful
+    /// </summary>
+    public bool Success { get; set; }
+
+    /// <summary>
+    /// Optional message providing additional context
+    /// </summary>
+    public string? Message { get; set; }
+
+    /// <summary>
+    /// The response data (structure varies by query type)
+    /// </summary>
+    public object? Data { get; set; }
+
+    /// <summary>
+    /// Error message if the operation failed
+    /// </summary>
+    public string? Error { get; set; }
+}

RoslynBridge.WebApi/Models/VSInstanceInfo.cs

@@ -0,0 +1,42 @@
+namespace RoslynBridge.WebApi.Models;
+
+/// <summary>
+/// Information about a registered Visual Studio instance
+/// </summary>
+public class VSInstanceInfo
+{
+    /// <summary>
+    /// The port number where this VS instance is listening
+    /// </summary>
+    public int Port { get; set; }
+
+    /// <summary>
+    /// The process ID of the Visual Studio instance
+    /// </summary>
+    public int ProcessId { get; set; }
+
+    /// <summary>
+    /// The solution file path (if any solution is open)
+    /// </summary>
+    public string? SolutionPath { get; set; }
+
+    /// <summary>
+    /// The solution name (if any solution is open)
+    /// </summary>
+    public string? SolutionName { get; set; }
+
+    /// <summary>
+    /// When this instance was registered
+    /// </summary>
+    public DateTime RegisteredAt { get; set; }
+
+    /// <summary>
+    /// Last heartbeat time
+    /// </summary>
+    public DateTime LastHeartbeat { get; set; }
+
+    /// <summary>
+    /// List of project names in the solution
+    /// </summary>
+    public List<string> Projects { get; set; } = new();
+}