Migrate analytics from SQLite to ClickHouse

SQLite was too slow for analytical aggregations on traffic_events and
waf_events (millions of rows, GROUP BY, COUNT DISTINCT). ClickHouse is
a columnar OLAP database purpose-built for this workload.

- Add ClickHouse container to Docker Compose with health check
- Create src/lib/clickhouse/client.ts with singleton client, table DDL,
  insert helpers, and all analytics query functions
- Update log-parser.ts and waf-log-parser.ts to write to ClickHouse
- Remove purgeOldEntries — ClickHouse TTL handles 90-day retention
- Rewrite analytics-db.ts and waf-events.ts to query ClickHouse
- Remove trafficEvents/wafEvents from SQLite schema, add migration
- CLICKHOUSE_PASSWORD is required (no hardcoded default)
- Update .env.example, README, and test infrastructure

API response shapes are unchanged — no frontend modifications needed.
Parse state (file offsets) remains in SQLite.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -20,6 +20,7 @@
     "test:e2e:headed": "playwright test --headed --config tests/playwright.config.ts"
   },
   "dependencies": {
+    "@clickhouse/client": "^1.18.2",
     "@radix-ui/react-accordion": "^1.2.12",
     "@radix-ui/react-avatar": "^1.1.11",
     "@radix-ui/react-checkbox": "^1.3.3",