feat(db): migrate from MySQL to PostgreSQL

Replace MySQL driver with pgx/v5 and pgxpool:
- Update sqlc to use postgresql engine
- Convert query.sql to PostgreSQL syntax ($1 params, CASE WHEN,
  ANY() arrays)
- Replace sql.DB with pgxpool.Pool throughout
- Change nullable types from sql.Null* to pgtype.*
- Update ID types from uint32 to int64 for PostgreSQL compatibility
- Delete MySQL-specific dynamic_connect.go
- Add opentelemetry.gowrap template for tracing

ntpdb/db.go

@@ -6,14 +6,15 @@ package ntpdb
 
 import (
 	"context"
-	"database/sql"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
 )
 
 type DBTX interface {
-	ExecContext(context.Context, string, ...interface{}) (sql.Result, error)
-	PrepareContext(context.Context, string) (*sql.Stmt, error)
-	QueryContext(context.Context, string, ...interface{}) (*sql.Rows, error)
-	QueryRowContext(context.Context, string, ...interface{}) *sql.Row
+	Exec(context.Context, string, ...interface{}) (pgconn.CommandTag, error)
+	Query(context.Context, string, ...interface{}) (pgx.Rows, error)
+	QueryRow(context.Context, string, ...interface{}) pgx.Row
 }
 
 func New(db DBTX) *Queries {
@@ -24,7 +25,7 @@ type Queries struct {
 	db DBTX
 }
 
-func (q *Queries) WithTx(tx *sql.Tx) *Queries {
+func (q *Queries) WithTx(tx pgx.Tx) *Queries {
 	return &Queries{
 		db: tx,
 	}