feat(mcp): migrate to Streamable HTTP transport (MCP spec 2025-03-26)

- Upgrade mcp-spring-webmvc from 0.10.0 to 0.18.1 (adds
  WebMvcStreamableServerTransportProvider alongside the legacy SSE provider)
- Add mcp-json-jackson2 0.18.1 for JacksonMcpJsonMapper adapter
- Exclude McpWebMvcServerAutoConfiguration (SSE transport) via
  spring.autoconfigure.exclude; register WebMvcStreamableServerTransportProvider
  and its RouterFunction manually in McpConfig so Spring AI's
  McpServerAutoConfiguration picks up the correct transport bean
- Remove sse-message-endpoint / sse-endpoint from application.yml;
  all MCP traffic now flows through POST+GET /mcp
- Remove McpSseMethodNotAllowed workaround from WebConfig and drop
  'sse' from SPA fallback exclusions (no longer needed)

Clients should connect with type: http at https://trueref.sal.giize.com/mcp

trueref-bootstrap/src/main/resources/application.yml

@@ -19,12 +19,13 @@ spring:
     locations: classpath:db/migration
   mvc:
     async:
-      request-timeout: 0   # SSE streams must not time out
-  # Spring AI MCP server. In Spring AI 1.0.0 the WebMVC transport is SSE-based
-  # (WebMvcSseServerTransportProvider) — the closest available transport to the 2025-03-26
-  # "Streamable HTTP" spec; there is no separate "protocol: streamable" property in this
-  # starter. JSON-RPC POSTs land on `sse-message-endpoint` (/mcp); server-initiated
-  # notifications stream over `sse-endpoint` (/sse). See com.trueref.adapter.in.mcp.
+      request-timeout: 0   # MCP GET streams must not time out
+  # Spring AI MCP server — Streamable HTTP transport (MCP spec 2025-03-26).
+  # McpWebMvcServerAutoConfiguration (SSE transport) is excluded below;
+  # WebMvcStreamableServerTransportProvider is wired manually in McpConfig.
+  # Clients connect with type: http at POST /mcp.
+  autoconfigure:
+    exclude: org.springframework.ai.mcp.server.autoconfigure.McpWebMvcServerAutoConfiguration
   ai:
     mcp:
       server:
@@ -32,8 +33,6 @@ spring:
         name: trueref
         version: 0.1.0
         type: SYNC
-        sse-message-endpoint: /mcp
-        sse-endpoint: /sse
 
 server:
   port: 8080