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>

strings/commands.py

@@ -73,6 +73,7 @@ CMD: dict[str, str] = {
     "fishsell":       "Müü kalu oma inventarist",
     "patchnotes":     "Vaata TipiBOTi viimaseid muudatusi ja uuendusi",
     "quests":         "Vaata oma päeva- ja nädalaülesandeid ning nõua auhinnad",
+    "consumables":    "Sirvi ja osta turgutusi (korduvostetavad boostid)",
 }
 
 # ---------------------------------------------------------------------------
@@ -90,6 +91,7 @@ OPT: dict[str, str] = {
     "give_kasutaja":      "Kellele annad?",
     "give_summa":         "Kui palju annad? ('all' = kogu saldo)",
     "buy_ese":            "Eseme nimi (vaata /shop)",
+    "consumable_ese":     "Turgutus, mida osta (tühjaks jättes näeb menüüd)",
     "rps_panus":          "Valikuline TipiCOINide panus ('all' = kogu saldo)",
     "rps_vastane":        "Väljakutse teisele mängijale (PvP)",
     "slots_panus":        "Panus TipiCOINides ('all' = kogu saldo)",