feat: add conditional asset embedding with dev/prod build separation

- Add embed-assets feature flag to make rust-embed/mime_guess optional
- Update Justfile with backend-dev command for development (no embedded assets)
- Add CORS middleware when assets not embedded (for Vite proxy)
- Improve db recipe with Bun script supporting start/reset/rm commands

Cargo.toml

@@ -4,6 +4,10 @@ version = "0.3.4"
 edition = "2024"
 default-run = "banner"
 
+[features]
+default = ["embed-assets"]
+embed-assets = ["dep:rust-embed", "dep:mime_guess"]
+
 [dependencies]
 anyhow = "1.0.99"
 async-trait = "0.1"
@@ -46,8 +50,8 @@ once_cell = "1.21.3"
 serde_path_to_error = "0.1.17"
 num-format = "0.4.4"
 tower-http = { version = "0.6.0", features = ["fs", "cors", "trace", "timeout"] }
-rust-embed = { version = "8.0", features = ["debug-embed", "include-exclude"] }
-mime_guess = "2.0"
+rust-embed = { version = "8.0", features = ["include-exclude"], optional = true }
+mime_guess = { version = "2.0", optional = true }
 clap = { version = "4.5", features = ["derive"] }
 rapidhash = "4.1.0"
 yansi = "1.0.1"