feat: complete Event Log, Ledger, Memory, Cascade Router, Upgrade Queue, Activity Feed

This commit implements six major features:

1. Event Log System (src/swarm/event_log.py)
   - SQLite-based audit trail for all swarm events
   - Task lifecycle tracking (created, assigned, completed, failed)
   - Agent lifecycle tracking (joined, left, status changes)
   - Integrated with coordinator for automatic logging
   - Dashboard page at /swarm/events

2. Lightning Ledger (src/lightning/ledger.py)
   - Transaction tracking for Lightning Network payments
   - Balance calculations (incoming, outgoing, net, available)
   - Integrated with payment_handler for automatic logging
   - Dashboard page at /lightning/ledger

3. Semantic Memory / Vector Store (src/memory/vector_store.py)
   - Embedding-based similarity search for Echo agent
   - Fallback to keyword matching if sentence-transformers unavailable
   - Personal facts storage and retrieval
   - Dashboard page at /memory

4. Cascade Router Integration (src/timmy/cascade_adapter.py)
   - Automatic LLM failover between providers (Ollama → AirLLM → API)
   - Circuit breaker pattern for failing providers
   - Metrics tracking per provider (latency, error rates)
   - Dashboard status page at /router/status

5. Self-Upgrade Approval Queue (src/upgrades/)
   - State machine for self-modifications: proposed → approved/rejected → applied/failed
   - Human approval required before applying changes
   - Git integration for branch management
   - Dashboard queue at /self-modify/queue

6. Real-Time Activity Feed (src/events/broadcaster.py)
   - WebSocket-based live activity streaming
   - Bridges event_log to dashboard clients
   - Activity panel on /swarm/live

Tests:
- 101 unit tests passing
- 4 new E2E test files for Selenium testing
- Run with: SELENIUM_UI=1 pytest tests/functional/ -v --headed

Documentation:
- 6 ADRs (017-022) documenting architecture decisions
- Implementation summary in docs/IMPLEMENTATION_SUMMARY.md
- Architecture diagram in docs/architecture-v2.md

docs/adr/018-lightning-ledger.md

@@ -0,0 +1,99 @@
+# ADR 018: Lightning Network Transaction Ledger
+
+## Status
+Accepted
+
+## Context
+The system needed to track all Lightning Network payments (incoming and outgoing) for accounting, dashboard display, and audit purposes. The existing payment handler created invoices but didn't persist transaction history.
+
+## Decision
+Implement a SQLite-based ledger (`ledger` table) that tracks all Lightning transactions with their lifecycle status.
+
+## Transaction Types
+
+| Type | Description |
+|------|-------------|
+| `incoming` | Invoice created (we're receiving payment) |
+| `outgoing` | Payment sent (we're paying someone) |
+
+## Transaction Status
+
+| Status | Description |
+|--------|-------------|
+| `pending` | Awaiting settlement |
+| `settled` | Payment completed |
+| `failed` | Payment failed |
+| `expired` | Invoice expired |
+
+## Schema
+```sql
+CREATE TABLE ledger (
+    id TEXT PRIMARY KEY,
+    tx_type TEXT NOT NULL,
+    status TEXT NOT NULL DEFAULT 'pending',
+    payment_hash TEXT UNIQUE NOT NULL,
+    amount_sats INTEGER NOT NULL,
+    memo TEXT,
+    invoice TEXT,
+    preimage TEXT,
+    source TEXT NOT NULL,
+    task_id TEXT,
+    agent_id TEXT,
+    created_at TEXT NOT NULL,
+    settled_at TEXT,
+    fee_sats INTEGER DEFAULT 0
+);
+```
+
+## Usage
+
+```python
+from lightning.ledger import (
+    create_invoice_entry,
+    mark_settled,
+    get_balance,
+)
+
+# Create invoice record
+entry = create_invoice_entry(
+    payment_hash=invoice.payment_hash,
+    amount_sats=1000,
+    memo="API access",
+    source="payment_handler",
+    task_id=task.id,
+)
+
+# Mark as paid
+mark_settled(payment_hash, preimage="secret")
+
+# Get balance
+balance = get_balance()
+print(f"Net: {balance['net_sats']} sats")
+```
+
+## Integration
+The `PaymentHandler` automatically:
+- Creates ledger entries when invoices are created
+- Updates status when payments are checked/settled
+- Tracks fees for outgoing payments
+
+## Balance Calculation
+```python
+{
+    "incoming_total_sats": total_received,
+    "outgoing_total_sats": total_sent,
+    "fees_paid_sats": total_fees,
+    "net_sats": incoming - outgoing - fees,
+    "pending_incoming_sats": pending_received,
+    "pending_outgoing_sats": pending_sent,
+    "available_sats": net - pending_outgoing,
+}
+```
+
+## Consequences
+- **Positive**: Complete payment history, balance tracking, audit trail
+- **Negative**: Additional DB writes, must keep in sync with actual Lightning node
+
+## Future Work
+- Reconciliation job to sync with LND node
+- Export to accounting formats (CSV, QIF)