Implement HTTP timeout configurations and enhance API documentation

- Added optional HTTP server timeout configurations (`HNHMAP_READ_TIMEOUT`, `HNHMAP_WRITE_TIMEOUT`, `HNHMAP_IDLE_TIMEOUT`) to `.env.example` and updated the server initialization in `main.go` to utilize these settings.
- Enhanced API documentation for the `rebuildZooms` endpoint to clarify its background processing and polling mechanism for status updates.
- Updated `configuration.md` to include new timeout environment variables for better configuration guidance.
- Improved error handling in the client for large request bodies, ensuring appropriate responses for oversized payloads.

frontend-nuxt/composables/useGravatarUrl.ts

@@ -1,8 +1,11 @@
 import md5 from 'md5'
 
+const gravatarCache = new Map<string, string>()
+
 /**
  * Returns Gravatar avatar URL for the given email, or empty string if no email.
  * Gravatar expects: trim, lowercase, then MD5 hex. Use empty string to show a placeholder (e.g. initial letter) in the UI.
+ * Results are memoized by (email, size) to avoid recomputing MD5 on every render.
  *
  * @param email - User email (optional)
  * @param size - Avatar size in pixels (default 64; navbar 32, drawer 40, profile 64–80)
@@ -10,7 +13,12 @@ import md5 from 'md5'
 export function useGravatarUrl(email: string | undefined, size?: number): string {
   const normalized = email?.trim().toLowerCase()
   if (!normalized) return ''
-  const hash = md5(normalized)
   const s = size ?? 64
-  return `https://www.gravatar.com/avatar/${hash}?s=${s}&d=identicon`
+  const key = `${normalized}\n${s}`
+  const cached = gravatarCache.get(key)
+  if (cached !== undefined) return cached
+  const hash = md5(normalized)
+  const url = `https://www.gravatar.com/avatar/${hash}?s=${s}&d=identicon`
+  gravatarCache.set(key, url)
+  return url
 }