Fix OTel wiring to match working Auth implementation

Three corrections vs Auth project:
- Replace AddOtlpExporter() (traces only) with UseOtlpExporter() so both
  traces and logs are exported via OTLP
- Remove redundant .WithLogging() call; builder.Logging.AddOpenTelemetry()
  is sufficient on its own
- Pass OTEL_EXPORTER_OTLP_ENDPOINT/PROTOCOL through from host env vars
  instead of hardcoding the collector URL

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

src/Budget.Api/Program.cs

@@ -10,6 +10,7 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using Microsoft.Extensions.Options;
 using Microsoft.IdentityModel.Tokens;
+using OpenTelemetry;
 using OpenTelemetry.Resources;
 using OpenTelemetry.Trace;
 
@@ -24,12 +25,11 @@ builder.Logging.AddOpenTelemetry(logging =>
 builder.Services.AddOpenTelemetry()
     .ConfigureResource(resource => resource
         .AddService(serviceName: "budget", serviceVersion: "1.0.0"))
-    .WithLogging()
     .WithTracing(tracing => tracing
         .AddAspNetCoreInstrumentation()
         .AddHttpClientInstrumentation()
-        .AddEntityFrameworkCoreInstrumentation()
-        .AddOtlpExporter());
+        .AddEntityFrameworkCoreInstrumentation())
+    .UseOtlpExporter();
 
 var connStr = builder.Configuration.GetConnectionString("DefaultConnection")
     ?? $"Host={builder.Configuration["POSTGRES_HOST"] ?? "localhost"};" +