feat(storage): add MinIO local storage and @manacore/shared-storage package

- Add MinIO service to docker-compose.dev.yml with auto-bucket initialization
- Create @manacore/shared-storage package with S3-compatible client
- Add factory functions for each project (Picture, Chat, ManaDeck, etc.)
- Include file utilities (generateFileKey, getContentType, validators)
- Update environment variables for S3/MinIO configuration
- Document storage architecture in CLAUDE.md

Local dev uses MinIO, production will use Hetzner Object Storage.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/shared-storage/package.json

@@ -0,0 +1,23 @@
+{
+	"name": "@manacore/shared-storage",
+	"version": "0.1.0",
+	"private": true,
+	"description": "S3-compatible object storage client for Manacore monorepo (MinIO local, Hetzner production)",
+	"main": "./src/index.ts",
+	"types": "./src/index.ts",
+	"exports": {
+		".": "./src/index.ts"
+	},
+	"scripts": {
+		"type-check": "tsc --noEmit",
+		"clean": "rm -rf dist"
+	},
+	"dependencies": {
+		"@aws-sdk/client-s3": "^3.700.0",
+		"@aws-sdk/s3-request-presigner": "^3.700.0"
+	},
+	"devDependencies": {
+		"@types/node": "^24.10.1",
+		"typescript": "^5.9.3"
+	}
+}