fix(telegram): fix claude client dispatch + strategy creation workflow

- telegram/bot.go: clientForProvider now returns NewClaudeClient() for
  'claude' provider (was incorrectly falling back to DeepSeekClient which
  uses OpenAI wire format, breaking Anthropic API calls)

- api/server.go: fix scan_interval_minutes schema default (3, not 60);
  POST /api/strategies now clearly states config is OPTIONAL with complete
  working defaults; POST /api/traders removes redundant GET workflow note

- telegram/agent/prompt.go: simplify strategy creation — just POST {name}
  without config (backend applies full working defaults automatically);
  only include config when user requests custom settings

telegram/bot.go

@@ -254,9 +254,12 @@ func clientForProvider(provider string) mcp.AIClient {
 		return mcp.NewOpenAIClient()
 	case "deepseek":
 		return mcp.NewDeepSeekClient()
+	case "claude":
+		// Anthropic Messages API — different wire format (x-api-key, input_schema, tool_use blocks).
+		return mcp.NewClaudeClient()
 	default:
-		// Qwen, Kimi, Grok, Gemini, Claude, custom: fall back to DeepSeek-format client.
-		// These providers use OpenAI-compatible APIs; CustomAPIURL and CustomModelName are required.
+		// Qwen, Kimi, Grok, Gemini, custom: OpenAI-compatible APIs.
+		// CustomAPIURL and CustomModelName are required for these providers.
 		return mcp.NewDeepSeekClient()
 	}
 }