feat: Major v2 rewrite with modern Ruby architecture and enhanced features

BREAKING CHANGES:
- Complete architectural overhaul from v4.x to v5.0.0
- Replaced entity system with simpler resources pattern
- Restructured client layer from client/ to clients/ directory
- Removed param builders in favor of integrated client logic
- Changed module structure and namespacing

New Features:
- Zeitwerk autoloading for modern Ruby module management
- Smart upload detection with automatic method selection
- Enhanced multipart upload with parallel processing support
- Progress tracking for all upload operations
- Batch upload capabilities with error handling per file
- CDN subdomain support for improved performance
- Comprehensive examples and integration tests

Improvements:
- Modern Ruby 3.0+ architecture with frozen string literals
- Centralized configuration with environment variable support
- Better error handling with ErrorHandler and ThrottleHandler mixins
- Thread-safe upload operations with configurable concurrency
- Extensive VCR test coverage for API operations
- Clean separation between REST and Upload API clients

Ruby 3.4+ Compatibility:
- Added addressable dependency (missing runtime dependency)
- Fixed gemspec require_paths (removed redundant paths)
- Added base64, bigdecimal, mutex_m gems for Ruby 3.4+ stdlib changes
- CI matrix already includes Ruby 3.4 testing

Technical Changes:
- 198 files changed (+11,500 additions, -5,000 deletions)
- Migrated from mimemagic to mime-types for MIME detection
- Replaced parallel/retries with built-in threading
- Removed uploadcare-api_struct dependency
- Added comprehensive YARD documentation structure

Author: vipulnsward

.gitignore

@@ -18,4 +18,6 @@ Gemfile.lock
 .ruby-version
 project_files
 *.gem
+.vscode/
+.DS_Store
 .claude/

.rubocop.yml

@@ -1,6 +1,7 @@
 AllCops:
   NewCops: enable
   TargetRubyVersion: 3.0
+  SuggestExtensions: false
 
 Layout/LineLength:
   Max: 120
@@ -10,24 +11,47 @@ Layout/LineLength:
 Lint/IneffectiveAccessModifier:
   Enabled: false
 
-Style/HashTransformKeys:
-  Exclude:
-    - 'lib/uploadcare/entity/decorator/paginator.rb'
-    - 'lib/uploadcare/client/conversion/video_conversion_client.rb'
-    - 'lib/uploadcare/entity/file.rb'
-
 Metrics/BlockLength:
   Exclude:
     - 'bin/'
     - 'spec/**/*'
     - 'uploadcare-ruby.gemspec'
 
+Metrics/ClassLength:
+  Max: 100
+  Exclude:
+    - 'lib/uploadcare/clients/upload_client.rb'  # Complex upload logic with 9 endpoints
+    - 'lib/uploadcare/resources/file.rb'  # Pre-existing file resource with many methods
+    - 'lib/uploadcare/uploader.rb'  # Uploader module with multiple upload strategies
+
 Metrics/ModuleLength:
+  Max: 100
   Exclude:
     - 'spec/**/*'
+    - 'lib/uploadcare/uploader.rb'  # Uploader module with multiple upload strategies
 
 Metrics/MethodLength:
   Max: 20
+  Exclude:
+    - 'lib/uploadcare/clients/upload_client.rb'  # Parallel upload requires coordination logic
+    - 'lib/uploadcare/uploader.rb'  # Parallel upload coordination
+
+Metrics/AbcSize:
+  Max: 17
+  Exclude:
+    - 'lib/uploadcare/clients/upload_client.rb'  # Upload methods have multiple parameters and validations
+    - 'lib/uploadcare/uploader.rb'  # Parallel upload coordination
+
+Metrics/CyclomaticComplexity:
+  Max: 7
+  Exclude:
+    - 'lib/uploadcare/clients/upload_client.rb'  # Upload logic has multiple conditional paths
+    - 'lib/uploadcare/uploader.rb'  # Parallel upload coordination
+
+Metrics/PerceivedComplexity:
+  Max: 8
+  Exclude:
+    - 'lib/uploadcare/clients/upload_client.rb'  # Parallel upload coordination is inherently complex
 
 Style/Documentation:
   Enabled: false

Gemfile

@@ -2,6 +2,11 @@
 
 source 'https://rubygems.org'
 
+# Ruby 3.4+ compatibility - these gems are no longer in stdlib
+gem 'base64'
+gem 'bigdecimal'
+gem 'mutex_m'
+
 gem 'byebug'
 gem 'rake'
 gem 'rspec'