feat(clienti): add Oracle XE PDB recreare scripts and audit cleanup

- Complete PDB export/import workflow (16 scripts in clienti/oracle-xe-21c/import/)
- Recreare PDB script with step-by-step guide (recreare_pdb.sql)
- Universal audit cleanup script for Oracle XE 11g-21c (cleanup_audit.sql)
- Troubleshooting guide with all lessons learned (depanare-ora-12954-spatiu.md)
- Fixed: DIRECTORY grant syntax, DBMS_LOCK grant, remap_tablespace USERS:ROA,
  impdp quoted AS SYSDBA for Windows, AWR retention 8 days, datafile full path
- Updated roa-windows-setup docs with XE prevention steps and gotchas table

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

clienti/oracle-xe-21c/import/07_sys_triggers.sql

@@ -0,0 +1,12 @@
+-- 07_sys_triggers.sql
+-- Create SYS custom triggers
+-- Source: backup/08_sys_triggers.sql
+
+CREATE OR REPLACE TRIGGER "SYS"."LOGON_AUDIT_TRIGGER"
+AFTER LOGON ON DATABASE
+BEGIN
+  DBMS_APPLICATION_INFO.SET_CLIENT_INFO(sys_context('userenv', 'ip_address'));
+  auth_pack.verifica_program();
+END;
+/
+ALTER TRIGGER "SYS"."LOGON_AUDIT_TRIGGER" ENABLE;