Guards vs Resolvers vs Interceptors (Clear Decision Guide)

Angular gives multiple tools that look similar, but their responsibilities are different.

## Guards
Purpose: decide if navigation is allowed  
Examples:
- user must be logged in
- user must have role admin
- prevent leaving page if unsaved changes

## Resolvers
Purpose: fetch required data before route activates  
Examples:
- load user profile before opening /profile
- load product details before /products/:id

## Interceptors
Purpose: modify or react to HTTP requests and responses  
Examples:
- attach JWT token
- handle 401 globally
- log request durations

## Decision table (easy)

- Navigation control = Guard
- Preload route data = Resolver
- HTTP cross-cutting behavior = Interceptor

> Next: Advanced RxJS patterns, retry, backoff, and caching API responses.