refactor(rules): consolidate type safety content and clean software development ruleset

- Remove duplicate content and restore file integrity in software_development.mdc
- Add comprehensive Type Safety Enforcement section to type_safety_guide.mdc
- Clean up file structure and eliminate corruption from duplicate sections
- Move type safety patterns and guidelines to appropriate specialized guide

.cursor/rules/development/type_safety_guide.mdc

@@ -40,6 +40,23 @@ Practical rules to keep TypeScript strict and predictable. Minimize exceptions.
 
    - Avoid `(obj as any)[k]`.
 
+## Type Safety Enforcement
+
+### Core Type Safety Rules
+- **No `any` Types**: Use explicit types or `unknown` with proper type guards
+- **Error Handling Uses Guards**: Implement and reuse type guards from `src/interfaces/**`
+- **Dynamic Property Access**: Use `keyof` + `in` checks for type-safe property access
+
+### Type Guard Patterns
+- **API Errors**: Use `isApiError(error)` guards for API error handling
+- **Database Errors**: Use `isDatabaseError(error)` guards for database operations
+- **Axios Errors**: Implement `isAxiosError(error)` guards for HTTP error handling
+
+### Implementation Guidelines
+- **Avoid Type Assertions**: Replace `as any` with proper type guards and interfaces
+- **Narrow Types Properly**: Use type guards to narrow `unknown` types safely
+- **Document Type Decisions**: Explain complex type structures and their purpose
+
 ## Minimal Special Cases (document in PR when used)
 
 - **Vue refs / instances**: Use `ComponentPublicInstance` or specific component