feat: add health check endpoints for Bot and Web

- Web: add /health endpoint with PostgreSQL readiness check (returns 200+JSON or 503)
- Web: add /alive endpoint for liveness probe
- Bot: add BotHealthCheckHostedService serving /health on port 8081 via HttpListener
- Bot: expose port 8081 in Dockerfile and install wget for healthcheck
- compose.yaml: add healthcheck sections for bot and web services
- tests: add TDD tests for both health endpoints

Bump version -> 1.16.0

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/GmRelay.Web/Program.cs

@@ -1,9 +1,13 @@
 using GmRelay.Web.Components;
+using GmRelay.Web.Health;
 using GmRelay.Web.Services;
 using Microsoft.AspNetCore.Authentication.Cookies;
 using Microsoft.AspNetCore.Authentication;
 using Microsoft.AspNetCore.DataProtection;
+using Microsoft.AspNetCore.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
 using System.Security.Claims;
+using System.Text.Json;
 using Telegram.Bot;
 using Npgsql;
 
@@ -12,6 +16,10 @@ var builder = WebApplication.CreateBuilder(args);
 // Add Aspire service defaults
 builder.AddServiceDefaults();
 
+// Add health checks
+builder.Services.AddHealthChecks()
+    .AddCheck<NpgsqlHealthCheck>("npgsql");
+
 // Add Data Protection
 builder.Services.AddDataProtection()
     .PersistKeysToFileSystem(new DirectoryInfo("/app/dataprotection-keys"));
@@ -83,6 +91,26 @@ app.MapStaticAssets();
 app.MapRazorComponents<App>()
     .AddInteractiveServerRenderMode();
 
+// Health check endpoints
+app.MapHealthChecks("/health", new HealthCheckOptions
+{
+    ResponseWriter = async (context, report) =>
+    {
+        context.Response.ContentType = "application/json";
+        var response = new
+        {
+            status = report.Status == HealthStatus.Healthy ? "healthy" : "unhealthy",
+            timestamp = DateTimeOffset.UtcNow.ToString("O")
+        };
+        await context.Response.WriteAsJsonAsync(response);
+    }
+});
+
+app.MapHealthChecks("/alive", new HealthCheckOptions
+{
+    Predicate = r => r.Tags.Contains("live")
+});
+
 // Endpoint to handle Telegram Login callback
 app.MapGet("/auth/telegram", async (HttpContext context, TelegramAuthService authService) =>
 {