feat(ai): implement AI memory system with context extraction and storage

Add comprehensive AI memory functionality including:
- Memory context preparation and caching
- Fact extraction from conversations
- Memory search and retrieval with category support
- JSON-based memory update operations (add/update/delete)
- Memory deduplication and normalization
- Integration with AI conversation flow

The system extracts relevant facts from conversations, stores them with
categories, and provides contextual memory to enhance AI responses.

Source/WulaFallenEmpire/EventSystem/AI/AIMemoryEntry.cs

@@ -0,0 +1,69 @@
+using System;
+
+namespace WulaFallenEmpire.EventSystem.AI
+{
+    /// <summary>
+    /// Represents a single memory entry extracted from conversations.
+    /// Inspired by Mem0's memory structure.
+    /// </summary>
+    public class AIMemoryEntry
+    {
+        /// <summary>Unique identifier for this memory</summary>
+        public string Id { get; set; }
+
+        /// <summary>The actual memory content/fact</summary>
+        public string Fact { get; set; }
+
+        /// <summary>
+        /// Category of memory: preference, personal, plan, colony, misc
+        /// </summary>
+        public string Category { get; set; }
+
+        /// <summary>Game ticks when this memory was created</summary>
+        public long CreatedTicks { get; set; }
+
+        /// <summary>Game ticks when this memory was last updated</summary>
+        public long UpdatedTicks { get; set; }
+
+        /// <summary>Number of times this memory has been accessed/retrieved</summary>
+        public int AccessCount { get; set; }
+
+        /// <summary>Hash of the fact for quick duplicate detection</summary>
+        public string Hash { get; set; }
+
+        public AIMemoryEntry()
+        {
+            Id = Guid.NewGuid().ToString("N").Substring(0, 12);
+            CreatedTicks = 0;
+            UpdatedTicks = 0;
+            AccessCount = 0;
+            Category = "misc";
+        }
+
+        public AIMemoryEntry(string fact, string category = "misc") : this()
+        {
+            Fact = fact;
+            Category = category ?? "misc";
+            Hash = ComputeHash(fact);
+        }
+
+        public static string ComputeHash(string text)
+        {
+            if (string.IsNullOrEmpty(text)) return "";
+            // Simple hash based on normalized text
+            string normalized = text.ToLowerInvariant().Trim();
+            return normalized.GetHashCode().ToString("X8");
+        }
+
+        public void UpdateFact(string newFact)
+        {
+            Fact = newFact;
+            Hash = ComputeHash(newFact);
+        }
+
+        public void MarkAccessed()
+        {
+            AccessCount++;
+        }
+    }
+}