Centralize credentials and make migration idempotent

- Move all DB credentials to config.asp with DSN/ODBC toggle
- Add Zabbix API URL and token to centralized config
- Update sql.asp, api.asp, apiusb.asp, zabbix.asp to use config
- Add GetConnectionString() and GetEmployeeConnectionString() functions
- Make migration SQL idempotent (safe to run multiple times)
- Add duplicate index cleanup (appname_2) to migration
- Document employee DB access limitation in CLAUDE.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apiusb.asp

@@ -1,30 +1,25 @@
 <%@ Language="VBScript" %>
 <%
+Option Explicit
+%>
+<!--#include file="includes/config.asp"-->
+<%
 '=============================================================================
 ' FILE: apiusb.asp
 ' PURPOSE: API endpoints for USB device operations
 ' SECURITY: Parameterized queries, JSON output
 ' CREATED: 2025-12-07
 '=============================================================================
-Option Explicit
 Response.ContentType = "application/json"
 Response.Charset = "utf-8"
 Response.Buffer = True
 
-' Create database connection directly (avoid sql.asp scoping issues)
-Dim objConn, DB_CONN_STRING
-DB_CONN_STRING = "Driver={MySQL ODBC 9.4 Unicode Driver};" & _
-                 "Server=192.168.122.1;" & _
-                 "Port=3306;" & _
-                 "Database=shopdb;" & _
-                 "User=570005354;" & _
-                 "Password=570005354;" & _
-                 "Option=3;" & _
-                 "Pooling=True;Max Pool Size=100;"
+' Database connection using centralized config
+Dim objConn
 
 On Error Resume Next
 Set objConn = Server.CreateObject("ADODB.Connection")
-objConn.ConnectionString = DB_CONN_STRING
+objConn.ConnectionString = GetConnectionString()
 objConn.Open
 
 If Err.Number <> 0 Then