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

commands/economy_extra_commands.py

@@ -13,6 +13,8 @@ from core import economy
 from core.emoji import EMOJI as E
 import strings as S
 
+from ._replies import reply_db_error
+
 
 def register_economy_extra_commands(
     tree: app_commands.CommandTree,
@@ -120,6 +122,9 @@ def register_economy_extra_commands(
                 return
             res = await economy.do_heist_check(interaction.user.id)
             if not res["ok"]:
+                if res["reason"] == "db_error":
+                    await reply_db_error(interaction)
+                    return
                 if res["reason"] == "banned":
                     await interaction.response.send_message(S.MSG_BANNED, ephemeral=True)
                 elif res["reason"] == "jailed":
@@ -270,6 +275,9 @@ def register_economy_extra_commands(
             return
         res = await economy.do_heist_check(interaction.user.id)
         if not res["ok"]:
+            if res["reason"] == "db_error":
+                await reply_db_error(interaction)
+                return
             if res["reason"] == "banned":
                 await interaction.response.send_message(S.MSG_BANNED, ephemeral=True)
             elif res["reason"] == "jailed":
@@ -518,6 +526,9 @@ def register_economy_extra_commands(
 
         res = await economy.do_give(interaction.user.id, kasutaja.id, summa_int)
         if not res["ok"]:
+            if res["reason"] == "db_error":
+                await reply_db_error(interaction)
+                return
             if res["reason"] == "banned":
                 await interaction.response.send_message(S.MSG_BANNED, ephemeral=True)
             elif res["reason"] == "jailed":
@@ -751,14 +762,13 @@ def register_economy_extra_commands(
     @tree.command(name="leaderboard", description=S.CMD["leaderboard"])
     async def cmd_leaderboard(interaction: discord.Interaction):
         await interaction.response.defer()
-        coins_raw, exp_raw, season_raw, prestige_raw, wagered_raw, fish_raw = await asyncio.gather(
-            economy.get_leaderboard(top_n=None),
-            economy.get_leaderboard_exp(top_n=None),
-            economy.get_leaderboard_season_exp(top_n=None),
-            economy.get_leaderboard_prestige(top_n=None),
-            economy.get_leaderboard_wagered(top_n=None),
-            economy.get_leaderboard_fish(top_n=None),
-        )
+        lbs = await economy.get_all_leaderboards()  # single collection scan for all six tabs
+        coins_raw = lbs["coins"]
+        exp_raw = lbs["exp"]
+        season_raw = lbs["season"]
+        prestige_raw = lbs["prestige"]
+        wagered_raw = lbs["wagered"]
+        fish_raw = lbs["fish"]
 
         house_entry = None
         regular = []
@@ -865,6 +875,9 @@ def register_economy_extra_commands(
     async def cmd_buy(interaction: discord.Interaction, ese: app_commands.Choice[str]):
         res = await economy.do_buy(interaction.user.id, ese.value)
         if not res["ok"]:
+            if res["reason"] == "db_error":
+                await reply_db_error(interaction)
+                return
             if res["reason"] == "banned":
                 await interaction.response.send_message(S.MSG_BANNED, ephemeral=True)
             elif res["reason"] == "owned":