feat(economy): add vanity shop and harden economy money-safety

Vanity shop (/vanity): cosmetic badges/titles as a pure whale coin sink -
purchases burn coins (not credited to the house) and equip a badge shown on
/profile. New vanity_owned/vanity_active fields, schema sync, and tests.

Money-safety and robustness fixes from a codebase review:

- _parse_amount now rejects negative amounts. Every bet/give/request flows
  through it, so a negative value can no longer mint coins on a loss/transfer
  path that trusts the caller's sign (all call sites already guarded <= 0;
  this closes the source).
- do_blackjack_payout no longer raises on a DB failure. The stake was already
  deducted in do_blackjack_bet, so it now logs critical with the owed amount
  (for admin reconciliation) and returns db_error; all payout call sites render
  a clear "payout failed" notice instead of crashing the interaction.
- Instant "kohv" consumable now cancels the pending reminder DMs for the
  cooldowns it wipes (via new INSTANT_RESET_COMMANDS), so no stale/duplicate
  reminders fire.
- Renamed the misleadingly-named _refund_user_safe -> _debit_house_safe (it
  debits the house) and dropped its ignored first arg.
- Added __all__ to vanity.py and consumables.py so `import *` no longer leaks
  incidental imports into the economy namespace.
- Documented Kõrvaklapid's +25 coin daily bonus in README and DEV_NOTES.

Tests: blackjack payout DB-failure safety and INSTANT_RESET_COMMANDS lockstep.

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

tests/test_consumables.py

@@ -100,3 +100,10 @@ class TestEffects:
         user = run(economy.get_user(UID))
         assert user["last_work"] is None      # cooldown wiped -> /work is ready
         assert economy.store._cooldown_remaining(user, "work") is None
+
+    def test_instant_reset_commands_match_cleared_cooldowns(self):
+        # The Discord layer cancels reminder DMs for exactly these commands after a
+        # kohv, so the list must stay in lockstep with the cooldown fields it wipes.
+        expected = tuple(f.removeprefix("last_") for f in economy.consumables._COOLDOWN_FIELDS)
+        assert economy.INSTANT_RESET_COMMANDS == expected
+        assert economy.INSTANT_RESET_COMMANDS == ("work", "beg", "crime", "rob", "fish")