Remove obsolete Vite configuration files that are no longer used by the build system
and update BUILDING.md to accurately reflect the current configuration structure.
**Removed Files:**
- vite.config.ts (47 lines) - Legacy configuration file
- vite.config.mts (70 lines) - Unused "main" configuration file
**Updated Documentation:**
- BUILDING.md - Corrected Vite configuration section to show actual usage
**Current Configuration Structure:**
- vite.config.web.mts - Used by build-web.sh
- vite.config.electron.mts - Used by build-electron.sh
- vite.config.capacitor.mts - Used by npm run build:capacitor
- vite.config.common.mts - Shared configuration utilities
- vite.config.utils.mts - Configuration utility functions
**Benefits:**
- Eliminates confusion about which config files to use
- Removes 117 lines of unused configuration code
- Documentation now matches actual build system usage
- Cleaner, more maintainable configuration structure
**Impact:**
- No functional changes to build process
- All platform builds continue to work correctly
- Reduced configuration complexity and maintenance overhead
