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>

sql/migration_cleanup_pc_types.sql

@@ -5,10 +5,13 @@
 -- ============================================================================
 --
 -- CHANGES:
--- 1. Add primary key to installedapps table
--- 2. Migrate machines using PC-specific machinetypes to generic PC (33) + pctypeid
--- 3. Update models to use generic PC machinetype
--- 4. Remove unused PC machinetypes (34-43, 45-46), keep USB Device (44)
+-- 1. Drop duplicate appname_2 index on applications table
+-- 2. Add primary key to installedapps table (if not exists)
+-- 3. Migrate machines using PC-specific machinetypes to generic PC (33) + pctypeid
+-- 4. Update models to use generic PC machinetype
+-- 5. Remove unused PC machinetypes (34-43, 45-46), keep USB Device (44)
+--
+-- NOTE: This migration is IDEMPOTENT - safe to run multiple times
 --
 -- RUN ON: Production database
 -- BACKUP FIRST: mysqldump -u root -p shopdb > shopdb_backup_$(date +%Y%m%d).sql
@@ -18,16 +21,42 @@
 START TRANSACTION;
 
 -- ============================================================================
--- 1. ADD PRIMARY KEY TO INSTALLEDAPPS TABLE
+-- 1. DROP DUPLICATE INDEX ON APPLICATIONS
 -- ============================================================================
-ALTER TABLE installedapps
-ADD COLUMN installedappid INT AUTO_INCREMENT PRIMARY KEY FIRST;
+-- Check if appname_2 index exists before dropping
+SET @index_exists = (SELECT COUNT(*) FROM information_schema.STATISTICS
+                     WHERE table_schema = DATABASE()
+                     AND table_name = 'applications'
+                     AND index_name = 'appname_2');
 
-SELECT 'Added PK to installedapps' AS status;
+SET @sql = IF(@index_exists > 0, 'DROP INDEX appname_2 ON applications', 'SELECT "Index appname_2 does not exist" AS status');
+PREPARE stmt FROM @sql;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
+SELECT IF(@index_exists > 0, 'Dropped duplicate appname_2 index', 'Index appname_2 already removed') AS status;
 
 -- ============================================================================
--- 2. MIGRATE MACHINES FROM PC-SPECIFIC TYPES TO GENERIC PC (33) + PCTYPEID
+-- 2. ADD PRIMARY KEY TO INSTALLEDAPPS TABLE (if not exists)
 -- ============================================================================
+SET @col_exists = (SELECT COUNT(*) FROM information_schema.COLUMNS
+                   WHERE table_schema = DATABASE()
+                   AND table_name = 'installedapps'
+                   AND column_name = 'installedappid');
+
+SET @sql = IF(@col_exists = 0,
+    'ALTER TABLE installedapps ADD COLUMN installedappid INT AUTO_INCREMENT PRIMARY KEY FIRST',
+    'SELECT "Column installedappid already exists" AS status');
+PREPARE stmt FROM @sql;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
+SELECT IF(@col_exists = 0, 'Added PK to installedapps', 'PK installedappid already exists') AS status;
+
+-- ============================================================================
+-- 3. MIGRATE MACHINES FROM PC-SPECIFIC TYPES TO GENERIC PC (33) + PCTYPEID
+-- ============================================================================
+-- These UPDATEs are already idempotent (won't change rows that don't match)
 
 -- PC - Standard (36) → machinetypeid=33, pctypeid=1 (Standard)
 UPDATE machines
@@ -64,11 +93,11 @@ UPDATE machines
 SET machinetypeid = 33, pctypeid = 4
 WHERE machinetypeid BETWEEN 34 AND 46 AND pctypeid IS NULL;
 
-SELECT CONCAT('Total machines now using machinetypeid 34-46: ',
+SELECT CONCAT('Total machines still using machinetypeid 34-46: ',
     (SELECT COUNT(*) FROM machines WHERE machinetypeid BETWEEN 34 AND 46)) AS status;
 
 -- ============================================================================
--- 3. UPDATE MODELS TO USE GENERIC PC MACHINETYPE (33)
+-- 4. UPDATE MODELS TO USE GENERIC PC MACHINETYPE (33)
 -- ============================================================================
 UPDATE models
 SET machinetypeid = 33
@@ -77,9 +106,10 @@ WHERE machinetypeid BETWEEN 34 AND 46;
 SELECT CONCAT('Updated ', ROW_COUNT(), ' models to generic PC type') AS status;
 
 -- ============================================================================
--- 4. DELETE REDUNDANT MACHINETYPES
+-- 5. DELETE REDUNDANT MACHINETYPES
 -- ============================================================================
 -- Keep 33 (PC) and 44 (USB Device), remove 34-43 and 45-46
+-- These DELETEs are already idempotent (won't delete if rows don't exist)
 
 DELETE FROM machinetypes WHERE machinetypeid BETWEEN 34 AND 43;
 SELECT CONCAT('Deleted ', ROW_COUNT(), ' machinetypes (34-43)') AS status;
@@ -101,10 +131,13 @@ WHERE m.pctypeid IS NOT NULL
 GROUP BY m.pctypeid
 ORDER BY count DESC;
 
+SELECT 'VERIFICATION - Applications indexes:' AS info;
+SELECT index_name, column_name FROM information_schema.STATISTICS
+WHERE table_schema = DATABASE() AND table_name = 'applications';
+
 -- ============================================================================
--- COMMIT (uncomment when ready to apply)
+-- COMMIT
 -- ============================================================================
 COMMIT;
--- ROLLBACK; -- Use this instead if something looks wrong
 
 SELECT 'Migration completed successfully!' AS status;