refactor: clean up verbose and redundant comments

Trim or remove comments that:
- State the obvious (function names already convey purpose)
- Repeat what the code clearly shows
- Are excessively long without adding value

Keep comments that explain *why*, not *what*.

internal/middleware/ratelimit.go

@@ -27,19 +27,12 @@ import (
 	"log/slog"
 )
 
-// RateLimitConfig controls per-IP rate limiting using a sliding window counter.
 type RateLimitConfig struct {
-	// Requests is the max number of requests allowed per window.
-	Requests int
-	// Window is the time window duration (e.g. "1m").
-	Window time.Duration
-	// CleanupInterval is how often stale entries are purged (default: 5m).
+	Requests        int
+	Window          time.Duration
 	CleanupInterval time.Duration
 }
 
-// RateLimit returns a middleware that limits requests per IP address.
-// Uses an in-memory sliding window counter. When the limit is exceeded,
-// responds with HTTP 429 and a Retry-After header.
 func RateLimit(cfg RateLimitConfig, logger *slog.Logger) func(http.Handler) http.Handler {
 	requests := cfg.Requests
 	if requests <= 0 {