mount: refresh and evict hot dir cache (#8174)

* mount: refresh and evict hot dir cache

* mount: guard dir update window and extend TTL

* mount: reuse timestamp for cache mark

* Apply suggestion from @gemini-code-assist[bot]

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* mount: make dir cache tuning configurable

* mount: dedupe dir update notices

* mount: restore invalidate-all cache helper

* mount: keep hot dir tuning constants

* mount: centralize cache state reset

* mount: mark refresh completion time

* mount: allow disabling idle eviction

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

weed/command/mount_std.go

@@ -270,6 +270,7 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 		RdmaReadOnly:      *option.rdmaReadOnly,
 		RdmaMaxConcurrent: *option.rdmaMaxConcurrent,
 		RdmaTimeoutMs:     *option.rdmaTimeoutMs,
+		DirIdleEvictSec:   *option.dirIdleEvictSec,
 	})
 
 	// create mount root