feat(economy): add /consumables shop of repeatable, expiring boosts

The economy had many coin faucets but almost no sinks: the /shop is
one-time ownership, and gambling/rob fines route to the house (which
players drain back via jackpots and heists), so they recirculate rather
than destroy coins. Result: steady inflation.

Add a consumables shop as a true recurring sink - buying destroys the
coins and grants a temporary boost, so there's always something to spend
on after gear is maxed:

  - Energiajook XL (500) - 1h of 2x earnings on /work, /beg, /crime
  - XP jook (500)        - 1h of 2x EXP
  - Kohv (300)           - instantly clears all cooldowns

Timed buffs live in a new active_buffs field ({kind: expiry_iso}), pruned
on read; rebuying extends the timer. Effects hook where they belong:
earn_mult in income.do_work/do_beg/do_crime, exp_buff_mult in
levels.award_exp; kohv is self-contained. New /consumables command browses
the menu (with active buffs) or buys a boost. Covered by 9 tests.

Note: active_buffs is a new PocketBase field - run
scripts/sync_pb_schema.py before deploying or buffs won't persist.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_consumables.py

@@ -0,0 +1,102 @@
+"""Tests for the consumables shop (repeatable, expiring coin sink)."""
+
+from datetime import datetime, timedelta, timezone
+
+from core import economy
+
+from conftest import run
+
+UID = 4242
+
+
+def _fixed_now(monkeypatch, dt: datetime):
+    # _clock is the time seam shared by every economy submodule
+    monkeypatch.setattr(economy.store, "_clock", lambda: dt)
+    return dt
+
+
+def _fund(fake_pb, amount: int) -> None:
+    run(economy.get_user(UID))
+    fake_pb.record_for(UID)["balance"] = amount
+
+
+class TestBuy:
+    def test_buy_earn_buff_deducts_and_activates(self, fake_pb):
+        _fund(fake_pb, 1000)
+        res = run(economy.do_buy_consumable(UID, "energy_xl"))
+        assert res["ok"] and not res["instant"]
+        assert res["balance"] == 500          # 1000 - 500 cost
+        user = run(economy.get_user(UID))
+        assert economy.earn_mult(user) == 2.0
+        assert economy.exp_buff_mult(user) == 1.0
+
+    def test_insufficient_funds_rejected(self, fake_pb):
+        _fund(fake_pb, 100)
+        res = run(economy.do_buy_consumable(UID, "energy_xl"))
+        assert not res["ok"] and res["reason"] == "insufficient"
+        assert res["need"] == 400
+        assert run(economy.get_user(UID))["balance"] == 100   # unchanged
+
+    def test_banned_rejected(self, fake_pb):
+        _fund(fake_pb, 1000)
+        fake_pb.record_for(UID)["eco_banned"] = True
+        res = run(economy.do_buy_consumable(UID, "energy_xl"))
+        assert not res["ok"] and res["reason"] == "banned"
+
+    def test_unknown_consumable(self, fake_pb):
+        _fund(fake_pb, 1000)
+        res = run(economy.do_buy_consumable(UID, "nope"))
+        assert not res["ok"] and res["reason"] == "not_found"
+
+
+class TestBuffLifecycle:
+    def test_buff_expires(self, fake_pb, monkeypatch):
+        t0 = _fixed_now(monkeypatch, datetime(2026, 8, 19, 12, tzinfo=timezone.utc))
+        _fund(fake_pb, 1000)
+        run(economy.do_buy_consumable(UID, "energy_xl"))
+        assert economy.earn_mult(run(economy.get_user(UID))) == 2.0
+        # 61 minutes later the 60-minute buff is gone
+        _fixed_now(monkeypatch, t0 + timedelta(minutes=61))
+        assert economy.earn_mult(run(economy.get_user(UID))) == 1.0
+
+    def test_rebuy_extends_duration(self, fake_pb, monkeypatch):
+        t0 = _fixed_now(monkeypatch, datetime(2026, 8, 19, 12, tzinfo=timezone.utc))
+        _fund(fake_pb, 2000)
+        run(economy.do_buy_consumable(UID, "energy_xl"))          # expiry = t0 + 60m
+        _fixed_now(monkeypatch, t0 + timedelta(minutes=30))
+        res = run(economy.do_buy_consumable(UID, "energy_xl"))    # extends, not resets
+        assert res["extended"] is True
+        # remaining should be ~90m (30m left + 60m added), not 60m
+        assert res["remaining"] > timedelta(minutes=85)
+
+
+class TestEffects:
+    def test_earn_buff_doubles_work(self, fake_pb, monkeypatch):
+        import random
+        _fixed_now(monkeypatch, datetime(2026, 8, 19, 12, tzinfo=timezone.utc))
+        _fund(fake_pb, 1000)
+        monkeypatch.setattr(random, "randint", lambda a, b: 50)
+        monkeypatch.setattr(random, "choice", lambda seq: seq[0])
+        monkeypatch.setattr(random, "random", lambda: 0.99)   # no energiajook luck
+        base = run(economy.do_work(UID))["earned"]
+        fake_pb.record_for(UID)["last_work"] = None            # clear cooldown
+        run(economy.do_buy_consumable(UID, "energy_xl"))
+        boosted = run(economy.do_work(UID))["earned"]
+        assert boosted == base * 2
+
+    def test_exp_buff_doubles_award(self, fake_pb):
+        _fund(fake_pb, 1000)
+        run(economy.do_buy_consumable(UID, "xp_potion"))
+        res = run(economy.award_exp(UID, 10))
+        assert res["gained"] == 20            # 10 * 2x exp buff
+
+    def test_kohv_clears_cooldowns(self, fake_pb, monkeypatch):
+        t0 = _fixed_now(monkeypatch, datetime(2026, 8, 19, 12, tzinfo=timezone.utc))
+        _fund(fake_pb, 1000)
+        rec = fake_pb.record_for(UID)
+        rec["last_work"] = t0.isoformat()     # on cooldown
+        res = run(economy.do_buy_consumable(UID, "kohv"))
+        assert res["ok"] and res["instant"]
+        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