refactor: unify docker deployment and restructure frontend architecture

This commit implements a unified Docker deployment strategy, moving from separate frontend and backend images to a single, multi-stage build image containing both services. It also introduces a major reorganization of the frontend directory structure and simplifies the environment configuration.

Key changes:
- **Deployment**: Added a multi-stage `Dockerfile` and `docker-entrypoint.sh` to package the Go backend and Nginx-served frontend into a single container.
- **CI/CD**: Updated GitHub Actions workflows (`ci-cd.yml`, `release.yml`) to build and push the new unified image instead of separate ones.
- **Frontend Refactor**: Reorganized `frontend/src/pages` into a domain-driven directory structure (e.g., `auth/`, `admin/`, `content/`, `communication/`, `productivity/`, `settings/`, `misc/`).
- **Configuration**: Simplified `.env.example` and updated `docker-compose.yml` to reflect the unified service model and single host port.
- **Cleanup**: Removed deprecated `docker-compose.demo.yml`, `docker-compose.prod.yml`, and various unused frontend components and services.
- **Backend**: Refactored configuration loading to use exported `GetDurationEnv` for better consistency.

.env.example

@@ -1,54 +1,16 @@
-# Server Configuration
-FRONTEND_PORT=3000
-FRONTEND_HOST_PORT=3900
-BACKEND_PORT=8080
-BACKEND_HOST_PORT=9000
-GIN_MODE=debug
+# Trackeep Configuration for Casa OS
+# Only required variables - everything else is auto-configured
 
-# Demo Mode Configuration
-# Set to true for demo mode (read-only with demo data)
-# Set to false for normal mode (full functionality)
-VITE_DEMO_MODE=true
-VITE_API_URL=http://localhost:9000
-FRONTEND_URL=http://localhost:3900
-PUBLIC_API_URL=http://localhost:9000
+# Host port for the application (default: 8080)
+HOST_PORT=8080
 
 # Database Configuration
-DB_TYPE=postgres
-DB_HOST=localhost
-DB_PORT=5432
-DB_HOST_PORT=5433
+DB_PASSWORD=your_secure_password_here
 DB_USER=trackeep
-DB_PASSWORD=your_password_here
 DB_NAME=trackeep
-DB_SSL_MODE=disable
 
 # DragonflyDB Configuration
-DRAGONFLY_ADDR=dragonfly:6379
-DRAGONFLY_PORT=6379
-DRAGONFLY_HOST_PORT=6380
 DRAGONFLY_PASSWORD=your_dragonfly_password_here
 
-# JWT Configuration (also used for encryption)
-# Generate a secure 64-character hex string using: openssl rand -hex 32
+# JWT Secret (generate with: openssl rand -hex 32)
 JWT_SECRET=your_jwt_secret_here_64_hex_characters_long_exactly
-# Token expiration time (e.g., 24h, 1h, 30m, 7d)
-JWT_EXPIRES_IN=24h
-
-# GitHub backup storage
-# Self-hosted Trackeep instances use the unified control service for GitHub sign-in
-# and GitHub App installation. No per-instance GitHub App credentials are required.
-GITHUB_BACKUP_ROOT=./data/github-backups
-GITHUB_BACKUP_TIMEOUT=10m
-
-# File Upload Configuration
-UPLOAD_DIR=./uploads
-MAX_FILE_SIZE=10485760
-
-# CORS Configuration
-CORS_ALLOWED_ORIGINS=*
-
-# Auto Update Configuration
-AUTO_UPDATE_CHECK=false
-UPDATE_CHECK_INTERVAL=24h
-PRERELEASE_UPDATES=false