Add SQLite visitor IP logging to /server_storage

Log visitor IPs and paths to a local SQLite database via the existing
analytics API route, persisted at /server_storage/visitors.db in Docker
(falls back to ./visitors.db in dev).

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

package.json

@@ -10,6 +10,7 @@
   },
   "dependencies": {
     "@tailwindcss/typography": "^0.5.19",
+    "better-sqlite3": "^12.6.2",
     "date-fns": "^4.1.0",
     "gray-matter": "^4.0.3",
     "next": "16.1.6",
@@ -22,6 +23,7 @@
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@types/better-sqlite3": "^7.6.13",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",