feat: landing page + logo, dev-mode banner + sync cap, non-blocking sync with progress splash

src/InboxIntel.Api/Controllers/AppInfoController.cs

@@ -0,0 +1,38 @@
+using Asp.Versioning;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace InboxIntel.Api.Controllers;
+
+/// <summary>
+/// Public metadata the SPA reads on load to decide whether to show the dev
+/// banner. devMode falls back to the hosting environment when App:DevMode is
+/// unset, and can be forced on/off via the App:DevMode config / App__DevMode env.
+/// </summary>
+[ApiController]
+[ApiVersion("1.0")]
+[Route("api/v{version:apiVersion}/app")]
+public class AppInfoController : ControllerBase
+{
+    private readonly IConfiguration _config;
+    private readonly IWebHostEnvironment _env;
+
+    public AppInfoController(IConfiguration config, IWebHostEnvironment env)
+    {
+        _config = config;
+        _env = env;
+    }
+
+    [HttpGet("info")]
+    [AllowAnonymous]
+    public IActionResult Info()
+    {
+        var devMode = _config.GetValue<bool?>("App:DevMode") ?? _env.IsDevelopment();
+        return Ok(new
+        {
+            environment = _env.EnvironmentName,
+            devMode,
+            maxMessages = _config.GetValue<int>("GmailSync:MaxMessages")
+        });
+    }
+}