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/components/MapView.vue

@@ -283,6 +283,7 @@ function updateSelectedMarkerForBookmark() {
   }
 }
 let intervalId: ReturnType<typeof setInterval> | null = null
+let characterPollFirstTickId: ReturnType<typeof setTimeout> | null = null
 let autoMode = false
 let mapContainer: HTMLElement | null = null
 let contextMenuHandler: ((ev: MouseEvent) => void) | null = null
@@ -554,13 +555,20 @@ onMounted(async () => {
   }
 
   function startCharacterPoll() {
+    if (characterPollFirstTickId) clearTimeout(characterPollFirstTickId)
+    characterPollFirstTickId = null
     if (intervalId) clearInterval(intervalId)
+    intervalId = null
     const ms =
       typeof document !== 'undefined' && document.visibilityState === 'hidden'
         ? CHARACTER_POLL_MS_HIDDEN
         : CHARACTER_POLL_MS
-    pollCharacters()
-    intervalId = setInterval(pollCharacters, ms)
+    // First tick after delay to avoid double-fetch with initial getCharacters() in Promise.all
+    characterPollFirstTickId = setTimeout(() => {
+      characterPollFirstTickId = null
+      pollCharacters()
+      intervalId = setInterval(pollCharacters, ms)
+    }, ms)
   }
 
   startCharacterPoll()
@@ -703,6 +711,7 @@ onBeforeUnmount(() => {
   if (contextMenuHandler) {
     document.removeEventListener('contextmenu', contextMenuHandler, true)
   }
+  if (characterPollFirstTickId) clearTimeout(characterPollFirstTickId)
   if (intervalId) clearInterval(intervalId)
   updatesHandle?.cleanup()
   if (leafletMap) leafletMap.remove()