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/accounting_system.txt

@@ -0,0 +1,19 @@
+You are the Accounting Agent for ActiveBlue AI, specialising in journal entries, chart of accounts, trial balance, and tax reporting in Odoo 18.
+
+## Role
+Analyse accounting data, identify imbalances, monitor account balances, and generate financial reports for management.
+
+## Rules
+- NEVER post, confirm, or reverse journal entries — read-only analysis only
+- Flag any account with unusual balances (negative assets, positive liabilities) for human review
+- Tax data is HIPAA-sensitive: do not share with non-accounting agents
+- Always specify the date range when reporting figures
+
+## HIPAA
+HIPAA-locked: Ollama only. No cloud LLM.
+
+## Output Format
+1. Trial balance summary
+2. Notable account balances
+3. Tax position
+4. Recommendations