feat: implement external API integration with static tide tables (task 32)

- Add in-memory caching for external API responses (6-hour expiration)
- Implement OpenWeatherMap integration for weather data
- Create static tide tables for 22 Irish coastal stations
- Add tide calculation based on semi-diurnal patterns and lunar cycles
- Implement water quality, beach quality, and biodiversity placeholder endpoints
- Add comprehensive API documentation (EXTERNAL_API_SETUP.md)
- Fix frontend WaterQualityIndicator crash
- Remove Redis dependency (using in-memory cache instead)
- All external data endpoints functional and tested

server/package.json

@@ -22,6 +22,7 @@
   "dependencies": {
     "@clerk/clerk-sdk-node": "^5.0.0",
     "@prisma/client": "^5.22.0",
+    "axios": "^1.13.2",
     "cors": "^2.8.5",
     "dotenv": "^16.4.5",
     "exifr": "^7.1.3",
@@ -29,6 +30,8 @@
     "express-validator": "^7.2.0",
     "helmet": "^8.0.0",
     "multer": "^1.4.5-lts.1",
+    "node-cron": "^4.2.1",
+    "redis": "^5.9.0",
     "zod": "^3.23.8"
   },
   "devDependencies": {
@@ -36,6 +39,7 @@
     "@types/express": "^5.0.0",
     "@types/multer": "^1.4.12",
     "@types/node": "^22.9.0",
+    "@types/node-cron": "^3.0.11",
     "prisma": "^5.22.0",
     "tsx": "^4.19.2",
     "typescript": "^5.6.3"