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

sqlc.yaml

@@ -2,16 +2,17 @@ version: "2"
 sql:
   - schema: "schema.sql"
     queries: "query.sql"
-    engine: "mysql"
+    engine: "postgresql"
+    strict_order_by: false
     gen:
       go:
         package: "ntpdb"
         out: "ntpdb"
+        sql_package: "pgx/v5"
         emit_json_tags: true
         emit_db_tags: true
         omit_unused_structs: true
         emit_interface: true
-        # emit_all_enum_values: true
         rename:
           servers.Ip: IP
         overrides: