feat(dashboard): LLM stats answer who/what spends tokens — member scope chips and spend breakdowns

The stats section was designed single-user: four global charts, no
attribution. Request metadata rows now carry the session's source and
the frame's agent_id/depth (additive ensure_column), denormalized at log
time by the LoggingModel from the owner's pool — off the turn's hot
path, degrading to NULLs, never to a lost row.

The dashboard gains member scope chips filtering every chart, and a
breakdown row splitting the range's billed tokens by member, kind
(chat / sub-agents / cron / system agents / channels), agent, model and
provider — a sub-agent's spend is attributed to the sub-agent itself.
Rows predating the columns group under 'older data'.

web/i18n/it.js

@@ -416,7 +416,6 @@ export default {
   'dashboard.stats.requests': 'Richieste {per}',
   'dashboard.stats.tokens':   'Token {per}',
   'dashboard.stats.latency':  'Latenza media (ms)',
-  'dashboard.stats.models':   'Modelli',
   'dashboard.stats.per_min':  '/ min',
   'dashboard.stats.per_hour': '/ h',
   'dashboard.stats.per_day':  '/ giorno',
@@ -432,6 +431,26 @@ export default {
   'dashboard.stats.chart.non_cached': 'Non in cache',
   'dashboard.stats.chart.cache_hit':  'Cache hit: {pct}%',
 
+  'dashboard.stats.scope.all':      'Tutti',
+  'dashboard.stats.sub.breakdown':  'Come si distribuisce la spesa nel periodo selezionato',
+  'dashboard.stats.by_user':        'Per membro',
+  'dashboard.stats.by_kind':        'Per tipo',
+  'dashboard.stats.by_agent':       'Per agente',
+  'dashboard.stats.by_model':       'Per modello',
+  'dashboard.stats.by_provider':    'Per provider',
+  'dashboard.stats.user_unknown':   'Sconosciuto',
+  'dashboard.stats.tip.requests':   'richieste',
+
+  'dashboard.stats.kind.web':                 'Chat',
+  'dashboard.stats.kind.mobile':              'Mobile',
+  'dashboard.stats.kind.telegram':            'Telegram',
+  'dashboard.stats.kind.cron':                'Attività pianificate',
+  'dashboard.stats.kind.sub_agent':           'Sub-agent',
+  'dashboard.stats.kind.event_triage':        'Triage eventi',
+  'dashboard.stats.kind.memory_lint':         'Lint memoria',
+  'dashboard.stats.kind.conversation_review': 'Revisione conversazioni',
+  'dashboard.stats.kind.unknown':             'Dati precedenti',
+
   'dashboard.hero.subtitle':  'Il tuo centro di comando AI — ricerca, codice, pianificazione e orchestrazione. Tutto in un unico posto.',
 
   'dashboard.banner.no_models.title':  'Nessun modello LLM configurato.',