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

README.md

@@ -348,6 +348,7 @@ The **ECONOMY** role is granted on your first EXP award (i.e. first successful e
 | `/reminders` | Toggle per-command DM notifications. Bot DMs you the moment each cooldown expires. |
 | `/quests` | Personal daily (3) and weekly (2) quests with progress bars and a claim button. |
 | `/achievements` | Milestone badges over your lifetime stats (work/wealth/gambling/crime/fishing/streaks/prestige). Each unlocks once and pays a one-time coin reward; opening the command claims any newly earned. |
+| `/lottery [amount]` | View the pot or buy tickets (200 ⬡ each, max 100/draw). One winner is drawn daily at 21:00 Tallinn time and takes the whole pot — more tickets = higher weighted chance. Coins are conserved (the pot equals total ticket spend). Announced in `LOTTERY_CHANNEL_ID` if set. |
 | `/fish` | Interactive fishing minigame. Cast, wait for bite, pull, then keep or sell. 2min cooldown (90s with Ussipurk). |
 | `/fishbook` | View your fish collection - all caught species, rarity, count, and current inventory amounts. |
 | `/fishsell` | Sell all fish currently in your inventory at once. |