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

core/economy/store.py

@@ -87,6 +87,26 @@ COOLDOWNS: dict[str, timedelta] = {
     "fish":   timedelta(minutes=2),
 }
 
+# Items that shorten a command's cooldown: command -> (item_id, reduced cooldown).
+# Single source of truth so the cooldown check (do_*), the reminder scheduler
+# (_maybe_remind) and the restart restore (_restore_reminders) never drift apart.
+ITEM_COOLDOWNS: dict[str, tuple[str, timedelta]] = {
+    "work":  ("monitor",     timedelta(minutes=40)),
+    "beg":   ("hiirematt",   timedelta(minutes=3)),
+    "daily": ("korvaklapid", timedelta(hours=18)),
+    "fish":  ("ussipurk",    timedelta(seconds=90)),
+}
+
+
+def effective_cooldown(cmd: str, items) -> timedelta | None:
+    """The cooldown for `cmd` given the user's owned `items`, applying any
+    item-based reduction. Returns None for commands with no cooldown."""
+    override = ITEM_COOLDOWNS.get(cmd)
+    if override is not None and override[0] in items:
+        return override[1]
+    return COOLDOWNS.get(cmd)
+
+
 JAIL_DURATION  = timedelta(minutes=30)
 HEIST_JAIL     = timedelta(hours=1, minutes=30)