feat: Add REST API handlers for exercises, plans, and sessions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/cmd/server/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"os"
+
+	"training-tracker/internal/api"
+	"training-tracker/internal/storage"
+)
+
+func main() {
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
+	slog.SetDefault(logger)
+
+	ctx := context.Background()
+
+	db, err := storage.NewDB(ctx)
+	if err != nil {
+		slog.Error("failed to connect to database", "error", err)
+		os.Exit(1)
+	}
+	defer db.Close()
+
+	if err := db.Migrate(ctx); err != nil {
+		slog.Error("failed to run migrations", "error", err)
+		os.Exit(1)
+	}
+	slog.Info("database migrations completed")
+
+	router := api.NewRouter(db)
+
+	port := os.Getenv("PORT")
+	if port == "" {
+		port = "8080"
+	}
+
+	slog.Info("server starting", "port", port)
+	if err := http.ListenAndServe(":"+port, router); err != nil {
+		slog.Error("server failed", "error", err)
+		os.Exit(1)
+	}
+}