fix: resolve all linting and formatting issues

- Fix error return value checks (errcheck)
- Fix unused parameters by using underscore prefix
- Add missing package comments to all packages
- Fix context key type issue in middleware (use typed contextKey)
- Replace deprecated trace.NewNoopTracerProvider with noop.NewTracerProvider
- Fix embedded field selector in database client
- Remove trailing whitespace
- Remove revive linter (as requested) to avoid stuttering warnings for public API interfaces

All linting and formatting checks now pass.

internal/infra/database/client.go

@@ -1,3 +1,4 @@
+// Package database provides database client and connection management.
 package database
 
 import (
@@ -20,11 +21,11 @@ type Client struct {
 
 // Config holds database configuration.
 type Config struct {
-	DSN              string
-	MaxConnections   int
-	MaxIdleConns     int
-	ConnMaxLifetime  time.Duration
-	ConnMaxIdleTime  time.Duration
+	DSN             string
+	MaxConnections  int
+	MaxIdleConns    int
+	ConnMaxLifetime time.Duration
+	ConnMaxIdleTime time.Duration
 }
 
 // NewClient creates a new Ent client with connection pooling.
@@ -46,7 +47,7 @@ func NewClient(cfg Config) (*Client, error) {
 	defer cancel()
 
 	if err := db.PingContext(ctx); err != nil {
-		db.Close()
+		_ = db.Close()
 		return nil, fmt.Errorf("failed to ping database: %w", err)
 	}
 
@@ -72,7 +73,7 @@ func (c *Client) Close() error {
 
 // Migrate runs database migrations.
 func (c *Client) Migrate(ctx context.Context) error {
-	return c.Client.Schema.Create(ctx)
+	return c.Schema.Create(ctx)
 }
 
 // Ping checks database connectivity.
@@ -84,4 +85,3 @@ func (c *Client) Ping(ctx context.Context) error {
 func (c *Client) DB() *sql.DB {
 	return c.db
 }
-