feat(weather)!: add /thuyvan flood alerts for Tân Thuận

/thuyvan shows the 5-day tide-peak forecast at Phú An and Nhà Bè from
the Đài KTTV Nam Bộ bulletin PDF, the Open-Meteo rain forecast, and live
VNDMS river gauges within 30 km. /thuyvan_subscribe opts a chat into a
10:30 ICT push, retried at 12:30, sent only when a forecast peak reaches
báo động I (1.40 m) or a day's rain reaches 50 mm. A missing or stale
bulletin fails the push instead of reading as no risk.

The thoitiet module is renamed to weather; the /thoitiet* commands keep
their names.

BREAKING CHANGE: the module key is now "weather". A MODULES list that
names thoitiet fails at startup and must name weather instead.

cmd/server/main.go

@@ -35,8 +35,8 @@ import (
 	"github.com/tiennm99/miti99bot/internal/modules/stats"
 	"github.com/tiennm99/miti99bot/internal/modules/sticker"
 	"github.com/tiennm99/miti99bot/internal/modules/stock"
-	"github.com/tiennm99/miti99bot/internal/modules/thoitiet"
 	"github.com/tiennm99/miti99bot/internal/modules/util"
+	"github.com/tiennm99/miti99bot/internal/modules/weather"
 	"github.com/tiennm99/miti99bot/internal/modules/wordle"
 	"github.com/tiennm99/miti99bot/internal/server"
 	"github.com/tiennm99/miti99bot/internal/storage"
@@ -106,7 +106,7 @@ func factories() map[string]modules.Factory {
 		sticker.CollectionName: sticker.New,
 		"alias":                alias.New,
 		"blacklist":            blacklist.New,
-		"thoitiet":             thoitiet.New,
+		weather.CollectionName: weather.New,
 	}
 }