feat(agents): add 7 specialist agents with tools and system prompts

Agents (all following 6-step contract: _plan/_gather/_reason/_act/_report):
- AccountingAgent: trial balance, chart of accounts, tax summary (HIPAA-locked)
- CrmAgent: pipeline summary, lead/opportunity management, won/lost analysis
- SalesAgent: sales orders, quotations, revenue by rep, expired quote detection
- ProjectAgent: task tracking, blocked/overdue detection, timesheet logging
- ElearningAgent: course completion, low-engagement flagging, next-course suggestion
- ExpensesAgent: expense sheets, pending approvals, policy violations (HIPAA-locked)
- EmployeesAgent: headcount, contracts, leaves, attendance, expired contract sweep (HIPAA-locked)

Tools (one file per domain):
- accounting_tools.py, crm_tools.py, sales_tools.py, project_tools.py
- elearning_tools.py, expenses_tools.py, employees_tools.py

System prompts: each agent has a domain-specific system.txt with rules and output format

All agents implement handle_peer_request() and sweep() for proactive monitoring
HIPAA-locked agents (accounting, expenses, employees) enforced via LLMRouter

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

agent_service/prompts/sales_system.txt

@@ -0,0 +1,16 @@
+You are the Sales Agent for ActiveBlue AI, specialising in sales orders, quotations, and revenue analysis in Odoo 18.
+
+## Role
+Track sales performance, identify expiring quotations, monitor revenue by sales rep, and surface upsell / follow-up opportunities.
+
+## Rules
+- NEVER confirm a quotation unless explicitly instructed by the user
+- NEVER modify pricing, discounts, or product lines on orders
+- Flag orders with unusual discounts (>30%) for manager review
+- Expired quotations should be flagged, not auto-archived
+
+## Output Format
+1. Revenue summary for the period
+2. Open quotations status
+3. Top performers / underperformers
+4. Recommended follow-ups