feat: Implement database migration framework with initial migrations for organizations, workspaces, agents, virtual hosts, upstreams, certificates, and users

docs/project-structure.md

@@ -169,14 +169,13 @@ nxmesh/
 │   │   ├── utils/               # Utilities
 │   │   └── styles/              # CSS/Tailwind
 │   └── public/
-│   
+│
 │   # Build output (dist/) is embedded into master binary
 │   # Master serves static files at root path ("/")
 │
-├── migrations/                  # Database migrations
-│   └── sea-orm/
-│       ├── Cargo.toml
-│       └── src/
+├── migration/                  # Database migrations
+│   ├── Cargo.toml
+│   └── src/
 │
 ├── tests/                       # Integration tests
 │   ├── integration/