Add chat-memory module: MessageWindowChatMemory, JDBC and Redis repositories, per-user conversation IDs

Real PostgreSQL 16 and Redis Stack 7.4; 24 tests write output/01-24. Covers the 20-message
default window with no property, the 36-character conversation_id, tool messages dropped by
JdbcChatMemoryRepository, concurrent add() on one conversation, a 1.x table under the 2.0
repository, the Redis repository silently backing off for a custom ChatMemory, and the
removal of PromptChatMemoryAdvisor.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Ja4jkzrbQ4LQZBNrb5mkZE

chat-memory/output/23-prompt-advisor-removed.txt

@@ -0,0 +1,21 @@
+# PromptChatMemoryAdvisor: Spring AI 1.1.8 vs 2.0.1
+
+$ javac PromptAdvisorFrom1x.java   # classpath: spring-ai-client-chat 2.0.1
+PromptAdvisorFrom1x.java:3: error: cannot find symbol
+import org.springframework.ai.chat.client.advisor.PromptChatMemoryAdvisor;
+                                                 ^
+  symbol:   class PromptChatMemoryAdvisor
+  location: package org.springframework.ai.chat.client.advisor
+PromptAdvisorFrom1x.java:10: error: cannot find symbol
+        return PromptChatMemoryAdvisor.builder(chatMemory).build();
+               ^
+  symbol:   variable PromptChatMemoryAdvisor
+  location: class PromptAdvisorFrom1x
+2 errors
+
+$ javac PromptAdvisorFrom1x.java   # classpath: spring-ai-client-chat 1.1.8 first
+PromptAdvisorFrom1x.java:10: warning: [removal] PromptChatMemoryAdvisor in org.springframework.ai.chat.client.advisor has been deprecated and marked for removal
+        return PromptChatMemoryAdvisor.builder(chatMemory).build();
+               ^
+1 warning
+compiled: PromptAdvisorFrom1x.class