fix: Odoo 18 field errors, routing quality, bot presence, and add architecture docs

- expenses_tools: remove 'date' from hr.expense.sheet field lists (Odoo 18
  uses accounting_date; querying 'date' raised ValueError at runtime)
- master_system.txt: add few-shot routing examples so Llama 3.1 8B correctly
  outputs agents=[] for general questions instead of defaulting to expenses_agent
- ab_ai_bot.py: increase bot presence last_poll offset from 90s to 10min so
  the green dot stays on between cron runs (cron fires every ~5min in practice,
  not every 20s as configured)
- ARCHITECTURE.md: full system documentation covering component layout, request
  flow, LLM routing, agent registry, access control, health/presence mechanism,
  known issues fixed today, and future self-healing concept

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent_service/tools/expenses_tools.py

@@ -31,7 +31,7 @@ class ExpensesTools:
             domain.append(('state', '=', state))
         if employee_id:
             domain.append(('employee_id', '=', employee_id))
-        fields = ['name', 'employee_id', 'state', 'total_amount', 'date',
+        fields = ['name', 'employee_id', 'state', 'total_amount',
                   'accounting_date', 'journal_id']
         return await self._o.search_read('hr.expense.sheet', domain, fields, limit=limit)
 
@@ -39,7 +39,7 @@ class ExpensesTools:
         return await self._o.search_read(
             'hr.expense.sheet',
             [('state', '=', 'submit')],
-            ['name', 'employee_id', 'total_amount', 'date'],
+            ['name', 'employee_id', 'total_amount', 'accounting_date'],
             limit=100,
         )