docs: update architecture documentation with user bookmarking feature and related changes
docs: Add backend architecture overview and structure documentation - Introduced "Backend Architecture Overview" document detailing the architecture of Waste Plus backend applications, including purpose, application landscape, common architecture foundations, and intentional differences. - Updated "_Sidebar.md" to include links to the new "Backend Architecture Overview" and "Profiles and Environment Separation" documents. - Added "Backend Structure" document outlining the code structure tree for both backend applications, including directory layout, naming conventions, and architectural rules. - Created "Profiles and Environment Separation" document explaining profile activation and environment separation for both backend applications, including common models, environment variable responsibilities, and recommended operating patterns.
feat: Add detailed error documentation for NR Waste Plus application - Introduced new error codes and descriptions for common issues: - G405: Method Not Allowed - G408: Request Timeout - G409: Conflict - G410: Gone - G413: Payload Too Large - G415: Unsupported Media Type - G422: Unprocessable Entity - G429: Too Many Requests - G500: Internal Server Error - G501: Not Implemented - G502: Bad Gateway - G503: Service Unavailable - G504: Gateway Timeout - P403: Insufficient Permissions - R600: Data Cannot Be Retrieved - U404: User Not Registered - Created an overarching error handling guide to assist users in understanding and resolving application errors.