fix(db): complete PostgreSQL integration in validation and cleaner services

OrderNumberResolver, validation, and cleaner services had incomplete
PostgreSQL support - they only handled SQL Server and MySQL, causing
PostgreSQL to fall through to MySQL code paths with invalid syntax
(backticks, ? placeholders) and missing schema.table name splitting.

Changes:
- Add PostgreSQL SQL generation ($N params, double-quoted identifiers)
  in OrderNumberResolver, validation-application-service,
  production-input-service, and validation-database
- Add PostgreSQL to database factory functions in validation-database
  and cleaner-application-service
- Add UPPER, LOWER, and 40+ common SQL functions to SQL_KEYWORDS to
  prevent prepareSql() from quoting them as identifiers

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

src/main/services/database/postgresql.ts

@@ -238,6 +238,53 @@ const SQL_KEYWORDS = new Set([
   'FIRST',
   'LAST',
 
+  // ==================== Scalar & String Functions ====================
+  'UPPER',
+  'LOWER',
+  'TRIM',
+  'LTRIM',
+  'RTRIM',
+  'BTRIM',
+  'SUBSTRING',
+  'CONCAT',
+  'LENGTH',
+  'CHAR_LENGTH',
+  'CHARACTER_LENGTH',
+  'REPLACE',
+  'POSITION',
+  'OVERLAY',
+  'LPAD',
+  'RPAD',
+  'REPEAT',
+  'REVERSE',
+  'SPLIT_PART',
+  'INITCAP',
+  'NORMALIZE',
+  'CHR',
+  'ASCII',
+  'FORMAT',
+
+  // ==================== Numeric Functions ====================
+  'ABS',
+  'CEIL',
+  'CEILING',
+  'FLOOR',
+  'ROUND',
+  'POWER',
+  'SQRT',
+  'MOD',
+  'SIGN',
+  'TRUNC',
+
+  // ==================== Date/Time Functions ====================
+  'EXTRACT',
+  'DATE_TRUNC',
+  'TO_CHAR',
+  'TO_DATE',
+  'TO_TIMESTAMP',
+  'TO_NUMBER',
+  'AGE',
+
   // ==================== Pattern Matching ====================
   'BETWEEN',
   'LIKE',