Truncate long values in client metadata logging

[coderabbitai]

Description

Implement truncation for long values in client metadata fields when logging tool invocations to prevent log inflation and improve readability.

Scope

Apply truncation to all client metadata fields logged in tool invocation messages:

• client_name
• client_version
• protocol_version
• meta_dict (all values within the dictionary)

Location

File: blockscout_mcp_server/tools/decorators.py
Lines: 42-49 (log message construction in log_tool_invocation decorator)

Context

Related to PR #316 discussion about logging the _meta field from MCP request context.

Backlinks

• PR: Extract _meta from request context #316
• Discussion: Extract _meta from request context #316 (comment)
• Requested by: @akolotov