feat(economy): add /lottery - daily draw, weighted winner takes the pot

Buy tickets (200 coins each, max 100/draw); one winner is drawn daily at 21:00
Tallinn time weighted by ticket count and credited the whole pot. Coin-conserving
by design: each ticket's cost is deducted at purchase and the winner is minted
exactly the sum of all ticket spend - no shared pot record, so no cross-period
race. Ticket state lives per-user keyed by draw period (full scan only at draw
time and for the pot view).

- New lottery.py: TICKET_COST/MAX_TICKETS/DRAW_HOUR, pure period_for, and
  do_buy_ticket / get_lottery_state / do_lottery_draw. New lottery_tickets +
  lottery_period schema fields (period added to _TEXT_FIELDS).
- /lottery [kogus] command (view or buy) with full failure handling.
- Scheduled lottery_draw_daily loop in bot.py (both profiles; each draws its own
  collection), announcing to the optional LOTTERY_CHANNEL_ID (config + .env).

14 tests: period boundary, buy/accumulate/reset/caps/guards, pot state, draw
payout with coin conservation, and the more-tickets-wins-more weighting.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013VbAVsrZuYesea99mPMmPT

strings/commands.py

@@ -80,6 +80,7 @@ CMD: dict[str, str] = {
     "bank":           "Vaata oma panka - röövikindel hoius",
     "deposit":        "Pane münte panka (röövikindel, aga ei teeni intressi)",
     "withdraw":       "Võta münte pangast rahakotti",
+    "lottery":        "Vaata TipiLOTO potti või osta pileteid (tühjaks jättes näeb infot)",
 }
 
 # ---------------------------------------------------------------------------
@@ -99,6 +100,7 @@ OPT: dict[str, str] = {
     "buy_ese":            "Eseme nimi (vaata /shop)",
     "deposit_summa":      "Kui palju panna panka? ('all' = kogu vaba raha)",
     "withdraw_summa":     "Kui palju pangast välja võtta? ('all' = kogu pangas)",
+    "lottery_kogus":      "Mitu piletit osta (tühjaks jättes näeb potti)",
     "consumable_ese":     "Turgutus, mida osta (tühjaks jättes näeb menüüd)",
     "vanity_ese":         "Tiitel, mida osta või kanda (tühjaks jättes näeb poodi)",
     "rps_panus":          "Valikuline TipiCOINide panus ('all' = kogu saldo)",
@@ -161,6 +163,7 @@ HELP_CATEGORIES: dict[str, dict] = {
             ("/withdraw <amount>", "Võta münte pangast rahakotti."),
             ("/quests", "Vaata oma päeva- ja nädalaülesandeid ning nõua auhinnad (uueneb iga päev/nädal)."),
             ("/achievements", "Vaata oma saavutusi. Iga lukust lahti saanud märk annab ühekordse müntipreemia."),
+            ("/lottery [kogus]", "Vaata TipiLOTO potti või osta pileteid. Loosimine iga päev - üks võitja saab kogu poti (rohkem pileteid = suurem võiduvõimalus)."),
             ("/leaderboard", "TipiBOTi edetabel - kes on kõige rikkam?"),
             ("/shop", "Sirvi TipiBOTi poodi"),
             ("/buy <item>", "Osta ese TipiBOTi poodist"),