Add AddMcpResourcesAndTools extension method

Extract the duplicated MCP resource and tool registrations
(BoardResources, CaptureResources, ProposalResources, ReadTools,
WriteTools, ProposalTools) into a shared extension method on
IMcpServerBuilder, eliminating triple-duplication across the
co-hosted web, standalone HTTP, and stdio hosting modes.

Part of #951 (DEBT-05).

Author: Chris0Jeky

backend/src/Taskdeck.Api/Extensions/McpResourcesAndToolsRegistration.cs

@@ -0,0 +1,27 @@
+using ModelContextProtocol.AspNetCore;
+using ModelContextProtocol.Server;
+using Taskdeck.Api.Mcp;
+
+namespace Taskdeck.Api.Extensions;
+
+/// <summary>
+/// Registers the shared set of MCP resources and tools used by all three
+/// hosting modes (co-hosted web, standalone HTTP, and stdio).
+/// </summary>
+public static class McpResourcesAndToolsRegistration
+{
+    /// <summary>
+    /// Add MCP resources (Board, Capture, Proposal) and tools (Read, Write, Proposal)
+    /// to the given MCP server builder.
+    /// </summary>
+    public static IMcpServerBuilder AddMcpResourcesAndTools(this IMcpServerBuilder builder)
+    {
+        return builder
+            .WithResources<BoardResources>()
+            .WithResources<CaptureResources>()
+            .WithResources<ProposalResources>()
+            .WithTools<ReadTools>()
+            .WithTools<WriteTools>()
+            .WithTools<ProposalTools>();
+    }
+}