Migrate Backend to Strict TypeScript

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Comprehensive TypeScript Type Safety Enhancement

Description

This PR implements a comprehensive TypeScript type safety enhancement across the entire codebase, progressively strengthening type checking from basic configurations to advanced type-safe interfaces and runtime validation.

Motivation

The codebase needed stronger type safety to improve developer experience, catch errors at compile time, and ensure runtime reliability. This systematic approach enables:

• Compile-time error detection through strict TypeScript compiler options
• Runtime safety with comprehensive validation using Zod
• Better developer experience with explicit typing and IDE support
• Code quality assurance through ESLint TypeScript rules

Key Changes

TypeScript Configuration

• Enabled strict compiler options: noImplicitAny, strictNullChecks, strictFunctionTypes, noImplicitReturns
• Configured project references for modular TypeScript builds
• Added explicit function return types throughout the codebase

Type System Enhancements

• Replaced any types with proper interfaces for better type safety
• Implemented branded types for IDs to prevent type confusion
• Created strict RPC interface definitions for API communication
• Separated domain and API types for better architectural boundaries

Runtime Validation & Safety

• Added runtime API validation using Zod schema validation
• Implemented type-safe event system interfaces with proper event handling
• Created comprehensive database entity type definitions
• Added class member accessibility modifiers for proper encapsulation

Development Experience

• Configured ESLint with TypeScript rules for consistent code quality
• Strengthened component boundary typing for better module isolation
• Added comprehensive event system documentation and examples

Impact

• 3,883 files changed with comprehensive type safety improvements
• Eliminated implicit any usage across the entire codebase
• Enhanced API reliability through runtime validation
• Improved developer productivity with better IDE support and compile-time error catching
• Established architectural boundaries between domain and API layers

📋 Complete Commit History (16 commits)

• 5a94a2d Implement Type-Safe Event System Interfaces
• 8fc0afa Add Class Member Accessibility Modifiers
• c0f23b2 Enable noImplicitReturns Compiler Option
• 8ec3f05 Implement Database Entity Type Definitions
• 9e48cf1 Configure TypeScript Project References
• 498435d Add Runtime API Validation
• c7d74d8 Separate Domain and API Types
• edee59d Create Branded Types for IDs
• 01f31c5 Enable strictFunctionTypes Compiler Option
• f4491af Add ESLint TypeScript Rules
• 1111b30 Strengthen Component Boundary Typing
• a46f596 Create Strict RPC Interface Definitions
• dcf006a Enable strictNullChecks Compiler Option
• cfa59ae Replace Any Types with Interfaces
• 03d0595 Add Explicit Function Return Types
• 3fe1aae Enable noImplicitAny Compiler Option

Testing

All changes maintain backward compatibility while enhancing type safety. The progressive approach ensures each enhancement builds upon the previous improvements without breaking existing functionality.

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