Move version display to GET /api/health/version in HealthController

Uses GetApplicationVersion(Assembly.GetExecutingAssembly()) — the same
timestamp-based version already logged at startup and baked into the
assembly via the csproj <Version> property. Removes the minimal-API
/version endpoint from web/Program.cs and reverts the web Dockerfile
APP_VERSION build-arg (no longer needed).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Apis/api/Controllers/HealthController.cs

@@ -1,5 +1,7 @@
+using System.Reflection;
 using Microsoft.AspNetCore.Cors;
 using Microsoft.AspNetCore.Mvc;
+using StartupHelpers;
 using Swashbuckle.AspNetCore.Annotations;
 
 namespace Api.Controllers
@@ -14,6 +16,18 @@ namespace Api.Controllers
     [EnableCors("FrontendOnly")]
     public sealed class HealthController : ControllerBase
     {
+        /// <summary>
+        /// Returns the deployed API version.
+        /// </summary>
+        /// <returns>200 OK with JSON payload: { "version": "1.0.0-build.20250522103045" }</returns>
+        // GET api/health/version
+        [HttpGet("version")]
+        [SwaggerOperation(Summary = "API version", Description = "Returns the deployed API assembly version.")]
+        [SwaggerResponse(StatusCodes.Status200OK, "Version returned")]
+        [ProducesResponseType(StatusCodes.Status200OK)]
+        public IActionResult Version() =>
+            Ok(new { version = StartupExtensions.GetApplicationVersion(Assembly.GetExecutingAssembly()) });
+
         /// <summary>
         /// Liveness probe.
         /// Indicates whether the process is running. Used by orchestration systems to confirm the process is alive.