fix: add missing formatDateTime import in SearchManager

The get_context_timeline mem-search function was broken due to
formatDateTime being used but not imported from timeline-formatting.ts.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -10,7 +10,7 @@
   "plugins": [
     {
       "name": "claude-mem",
-      "version": "7.4.4",
+      "version": "7.4.5",
       "source": "./plugin",
       "description": "Persistent memory system for Claude Code - context compression across sessions"
     }