feat: Migrate CLI architecture from external CLI shard to Crystal standard library

🔥 BREAKING CHANGE: Complete CLI architecture rewrite

## Major Changes

### Core Architecture
- Replace ::Cli::Supercommand with custom AmberCLI::Core::BaseCommand
- Implement AmberCLI::Core::CommandRegistry for command management
- Use Crystal's native OptionParser instead of external CLI parsing
- Remove CLI shard and shell-table dependencies from shard.yml

### Commands Migrated
- ✅ new: Create new Amber applications
- ✅ database: Database operations and migrations
- ✅ routes: Display application routes (custom table rendering)
- ✅ watch: Development server with file watching
- ✅ encrypt: Environment file encryption
- ✅ exec: Execute Crystal code in application context
- ✅ plugin: Generate application plugins
- ✅ pipelines: Show application pipelines and plugs

### Enhanced Features
- Improved error handling and user feedback
- Consistent command option parsing across all commands
- Native Crystal colorized output
- Better help system with detailed descriptions
- Integrated file watching with sentry functionality

### Testing & Quality
- Update all command specs for new architecture
- Fix YAML/JSON parsing in generator configuration
- Improve template engine with naming conventions support
- All tests passing with comprehensive coverage

### Benefits
- Zero external CLI dependencies
- Faster compilation and smaller binary size
- Clean, maintainable code structure
- Better error messages and user experience
- Foundation for future CLI enhancements

Closes major architectural debt and establishes solid foundation for Amber CLI v2.0

Author: crimson-knight

shard.yml

@@ -35,16 +35,6 @@ dependencies:
     github: crystal-loot/exception_page
     version: ~> 0.2.1
 
-  # Fork from Mosop, only used by the CLI tool
-  cli:
-    github: amberframework/cli
-    version: ~> 0.11.3
-
-  # Only used in the CLI tool, original appears to have been abandoned. Lucky one is maintained, mostly?
-  shell-table:
-    github: luckyframework/shell-table.cr
-    version: ~> 0.9.3
-
   # Latest version unknown, no updates since. 
   ## Worth moving into CLI tool
   inflector: