Add Oracle 18c sqlnet.ora config for old ODBC/Instant Client 11g compatibility

- Add config/sqlnet.ora with ALLOWED_LOGON_VERSION=8 for old client support
- Add scripts/fix-sqlnet.sh startup script to persist config across container restarts
- Update README with ORA-28040 troubleshooting, ODBC connection params, and deployment instructions
- Fix SID description: Oracle 18c has PDB (XEPDB1), not non-CDB
- Update container recreation instructions with startup scripts volume

Resolves ORA-28040: No matching authentication protocol when connecting
from Windows ODBC with Oracle Instant Client 11.2

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

proxmox/lxc108-oracle/config/sqlnet.ora

@@ -0,0 +1,18 @@
+# =============================================================================
+# sqlnet.ora - Configurare Oracle 18c XE pentru clienți vechi
+# =============================================================================
+# Locație în container: /opt/oracle/oradata/dbconfig/sqlnet.ora
+# Copiat automat în:    /opt/oracle/product/18c/dbhomeXE/network/admin/sqlnet.ora
+#                       de către fix-sqlnet.sh la pornirea containerului
+#
+# Problema rezolvată: ORA-28040: No matching authentication protocol
+# Permite conexiuni de la Oracle Instant Client 11g și ODBC vechi
+# =============================================================================
+
+NAMES.DIRECTORY_PATH = (EZCONNECT, TNSNAMES)
+
+# Suport pentru clienți vechi (Oracle 11g, Instant Client 11.2, ODBC vechi)
+# Valori posibile: 8, 10, 11, 12 (default în Oracle 18c este 12)
+# Versiunea 8 permite cele mai vechi clienți
+SQLNET.ALLOWED_LOGON_VERSION_SERVER=8
+SQLNET.ALLOWED_LOGON_VERSION_CLIENT=8