Add complete XML doc and Swagger annotations to all controller endpoints

Every public action now has <summary>, <param>, and <returns> XML docs
plus matching SwaggerOperation/SwaggerResponse attributes with typed response
descriptions. Class-level summaries added to CvController, JobSearchController,
and RagController. Explanatory inline comments removed from FileDownloadController
per project conventions.

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

Apis/api/Controllers/HealthController.cs

@@ -17,9 +17,11 @@ namespace Api.Controllers
     public sealed class HealthController : ControllerBase
     {
         /// <summary>
-        /// Returns the deployed API version.
+        /// Returns the deployed API version baked into the assembly at build time.
+        /// The version format is <c>1.0.0-build.{yyyyMMddHHmmss}</c> as defined in <c>api.csproj</c>.
+        /// Used by the web frontend to display the running build in the page footer.
         /// </summary>
-        /// <returns>200 OK with JSON payload: { "version": "1.0.0-build.20250522103045" }</returns>
+        /// <returns>200 OK with JSON payload: <c>{ "version": "1.0.0-build.20250522103045" }</c>.</returns>
         // GET api/health/version
         [HttpGet("version")]
         [SwaggerOperation(Summary = "API version", Description = "Returns the deployed API assembly version.")]