feat(通知模板): 支持 case 取值映射与事件名匹配渲染

Motivation:
让通知模板能够将 action、event 等原始枚举值映射为可读中文文案，并支持按事件名后缀匹配；同时简化 SafeW 消息发送格式，避免 Markdown 转义引入的显示问题。

Changes:

* 新增 `case` 模板函数，按值匹配 key/文案并支持末尾奇数参数作为默认值
* `case` 匹配兼容事件名后缀（如 trade.close 匹配 .close）
* `line` 前缀自动去除末尾冒号，避免重复冒号
* 模板渲染前自动注入 event 字段，便于模板按事件名取值
* SafeW 消息改为纯文本发送，移除 MarkdownV2 转义

internal/adapter/safew_test.go

@@ -11,32 +11,6 @@ import (
 	"aiaa-notification-service/internal/config"
 )
 
-func TestEscapeMarkdownV2(t *testing.T) {
-	tests := []struct {
-		name string
-		in   string
-		want string
-	}{
-		{name: "underscore and dot", in: "hello_world.", want: `hello\_world\.`},
-		{name: "empty", in: "", want: ""},
-		{name: "no specials", in: "hello", want: "hello"},
-		{name: "backslash first", in: `a\b`, want: `a\\b`},
-		{
-			name: "all specials",
-			in:   "_*[]()~`>#+-=|{}.!\\",
-			want: "\\_\\*\\[\\]\\(\\)\\~\\`\\>\\#\\+\\-\\=\\|\\{\\}\\.\\!\\\\",
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got := escapeMarkdownV2(tt.in)
-			if got != tt.want {
-				t.Fatalf("escapeMarkdownV2(%q) = %q, want %q", tt.in, got, tt.want)
-			}
-		})
-	}
-}
-
 func TestNewSenderSafew(t *testing.T) {
 	s, err := NewSender("safew", &config.SMTPConfig{}, nil)
 	if err != nil {
@@ -72,10 +46,10 @@ func TestSafeWSenderSendSuccess(t *testing.T) {
 	if gotBody["chat_id"] != "123456789" {
 		t.Fatalf("chat_id = %#v, want \"123456789\"", gotBody["chat_id"])
 	}
-	if gotBody["parse_mode"] != "MarkdownV2" {
-		t.Fatalf("parse_mode = %#v, want MarkdownV2", gotBody["parse_mode"])
+	if gotBody["parse_mode"] != nil && gotBody["parse_mode"] != "" {
+		t.Fatalf("parse_mode = %#v, want omitted/plain", gotBody["parse_mode"])
 	}
-	wantText := "*" + escapeMarkdownV2("hello_world.") + "*\n" + escapeMarkdownV2("price=1.5")
+	wantText := "hello_world.\nprice=1.5"
 	if gotBody["text"] != wantText {
 		t.Fatalf("text = %#v, want %#v", gotBody["text"], wantText)
 	}