fix(economy): handle db_error in commands, dedupe cooldowns, single leaderboard scan

Three robustness/perf fixes from the review:

1. db_error UX: economy core returns {"ok": False, "reason": "db_error"} on a
   PocketBase outage, but no handler expected it - deferred commands hung on
   "thinking..." and others showed a misleading "you're broke". Added a shared
   reply_db_error helper (commands/_replies.py) + S.ERR["db_error"], and wired a
   db_error branch into every handler that can receive it (daily/work/beg/crime/
   rob/give/buy/roulette/slots/blackjack/heist/fish/prestige/vanity/consumables/
   request-funding). Also fixed a latent KeyError in vs-bot RPS that read
   res["balance"] without checking res["ok"].

2. Deduped the item->cooldown mapping that was copied in do_daily/do_work/do_beg,
   do_fish_start, _maybe_remind and _restore_reminders. Single source of truth:
   store.ITEM_COOLDOWNS + effective_cooldown(cmd, items).

3. /leaderboard did six full-collection scans (one per tab). Added
   get_all_leaderboards() which scans once and builds all six views in memory.

Tests: effective_cooldown cases, and get_all_leaderboards matches the individual
queries + scans the collection exactly once.

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

tests/test_economy_pure.py

@@ -35,6 +35,29 @@ class TestLevels:
         assert economy.level_role_name(99) == "TipiLEGEND"
 
 
+class TestEffectiveCooldown:
+    def test_default_when_no_item(self):
+        assert economy.effective_cooldown("work", []) == economy.COOLDOWNS["work"]
+        assert economy.effective_cooldown("daily", []) == economy.COOLDOWNS["daily"]
+
+    def test_item_reduces_cooldown(self):
+        assert economy.effective_cooldown("work", ["monitor"]) == timedelta(minutes=40)
+        assert economy.effective_cooldown("beg", ["hiirematt"]) == timedelta(minutes=3)
+        assert economy.effective_cooldown("daily", ["korvaklapid"]) == timedelta(hours=18)
+        assert economy.effective_cooldown("fish", ["ussipurk"]) == timedelta(seconds=90)
+
+    def test_unrelated_item_does_not_reduce(self):
+        assert economy.effective_cooldown("work", ["hiirematt"]) == economy.COOLDOWNS["work"]
+
+    def test_command_without_cooldown_returns_none(self):
+        assert economy.effective_cooldown("unknown", []) is None
+
+    def test_every_item_cooldown_beats_its_base(self):
+        # An item-reduced cooldown must always be shorter than the base.
+        for cmd, (item, reduced) in economy.store.ITEM_COOLDOWNS.items():
+            assert reduced < economy.COOLDOWNS[cmd]
+
+
 class TestGambleExp:
     def test_tiers(self):
         assert economy.gamble_exp(0) == 0