feat: comprehensive module system and database management improvements

This commit introduces major enhancements to the module installation system,
database management, and configuration handling for AzerothCore deployments.

## Module System Improvements

### Module SQL Staging & Installation
- Refactor module SQL staging to properly handle AzerothCore's sql/ directory structure
- Fix SQL staging path to use correct AzerothCore format (sql/custom/db_*/*)
- Implement conditional module database importing based on enabled modules
- Add support for both cpp-modules and lua-scripts module types
- Handle rsync exit code 23 (permission warnings) gracefully during deployment

### Module Manifest & Automation
- Add automated module manifest generation via GitHub Actions workflow
- Implement Python-based module manifest updater with comprehensive validation
- Add module dependency tracking and SQL file discovery
- Support for blocked modules and module metadata management

## Database Management Enhancements

### Database Import System
- Add db-guard container for continuous database health monitoring and verification
- Implement conditional database import that skips when databases are current
- Add backup restoration and SQL staging coordination
- Support for Playerbots database (4th database) in all import operations
- Add comprehensive database health checking and status reporting

### Database Configuration
- Implement 10 new dbimport.conf settings from environment variables:
  - Database.Reconnect.Seconds/Attempts for connection reliability
  - Updates.AllowedModules for module auto-update control
  - Updates.Redundancy for data integrity checks
  - Worker/Synch thread settings for all three core databases
- Auto-apply dbimport.conf settings via auto-post-install.sh
- Add environment variable injection for db-import and db-guard containers

### Backup & Recovery
- Fix backup scheduler to prevent immediate execution on container startup
- Add backup status monitoring script with detailed reporting
- Implement backup import/export utilities
- Add database verification scripts for SQL update tracking

## User Import Directory

- Add new import/ directory for user-provided database files and configurations
- Support for custom SQL files, configuration overrides, and example templates
- Automatic import of user-provided databases and configs during initialization
- Documentation and examples for custom database imports

## Configuration & Environment

- Eliminate CLIENT_DATA_VERSION warning by adding default value syntax
- Improve CLIENT_DATA_VERSION documentation in .env.template
- Add comprehensive database import settings to .env and .env.template
- Update setup.sh to handle new configuration variables with proper defaults

## Monitoring & Debugging

- Add status dashboard with Go-based terminal UI (statusdash.go)
- Implement JSON status output (statusjson.sh) for programmatic access
- Add comprehensive database health check script
- Add repair-storage-permissions.sh utility for permission issues

## Testing & Documentation

- Add Phase 1 integration test suite for module installation verification
- Add comprehensive documentation for:
  - Database management (DATABASE_MANAGEMENT.md)
  - Module SQL analysis (AZEROTHCORE_MODULE_SQL_ANALYSIS.md)
  - Implementation mapping (IMPLEMENTATION_MAP.md)
  - SQL staging comparison and path coverage
  - Module assets and DBC file requirements
- Update SCRIPTS.md, ADVANCED.md, and troubleshooting documentation
- Update references from database-import/ to import/ directory

## Breaking Changes

- Renamed database-import/ directory to import/ for clarity
- Module SQL files now staged to AzerothCore-compatible paths
- db-guard container now required for proper database lifecycle management

## Bug Fixes

- Fix module SQL staging directory structure for AzerothCore compatibility
- Handle rsync exit code 23 gracefully during deployments
- Prevent backup from running immediately on container startup
- Correct SQL staging paths for proper module installation

import/db/examples/custom_npcs.sql

@@ -0,0 +1,18 @@
+-- Example: Add a custom NPC vendor
+-- This file demonstrates how to add a custom NPC to your world database
+
+-- Add the NPC template
+INSERT INTO `creature_template` (`entry`, `name`, `subname`, `minlevel`, `maxlevel`, `faction`, `npcflag`, `scale`, `unit_class`, `unit_flags`, `type`, `type_flags`, `InhabitType`, `RegenHealth`, `flags_extra`, `ScriptName`) 
+VALUES 
+(900000, 'Custom Vendor', 'Example NPC', 80, 80, 35, 128, 1, 1, 0, 7, 0, 3, 1, 2, '');
+
+-- Add the NPC spawn location (Stormwind Trade District)
+INSERT INTO `creature` (`guid`, `id1`, `map`, `position_x`, `position_y`, `position_z`, `orientation`, `spawntimesecs`, `MovementType`) 
+VALUES 
+(900000, 900000, 0, -8833.38, 628.628, 94.0066, 0.715585, 300, 0);
+
+-- Add some items to sell (optional)
+-- INSERT INTO `npc_vendor` (`entry`, `item`, `maxcount`, `incrtime`, `ExtendedCost`)
+-- VALUES 
+-- (900000, 2901, 0, 0, 0),  -- Mining Pick
+-- (900000, 5956, 0, 0, 0);  -- Blacksmith Hammer