feat: add network backend abstraction with gvproxy and port reconciliation (B20)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lightsofapollo

crates/Cargo.lock

@@ -14,5 +14,8 @@ thiserror = { workspace = true }
 tracing = { workspace = true }
 rusqlite = { version = "0.34", features = ["bundled"] }
 
+[dev-dependencies]
+tempfile = { workspace = true }
+
 [lints]
 workspace = true

crates/vz-stack/Cargo.toml

@@ -12,4 +12,8 @@ pub enum StackError {
     /// Invalid stack specification.
     #[error("invalid stack spec: {0}")]
     InvalidSpec(String),
+
+    /// Network backend operation failed.
+    #[error("network error: {0}")]
+    Network(String),
 }

crates/vz-stack/src/error.rs

@@ -8,13 +8,18 @@
 
 mod error;
 mod events;
+mod network;
 mod reconcile;
 mod spec;
 mod state_store;
 mod volume;
 
 pub use error::StackError;
 pub use events::{EventRecord, StackEvent};
+pub use network::{
+    GvproxyBackend, GvproxyConfig, NetworkBackend, NetworkHandle, PortConflict, PublishedPort,
+    detect_port_conflicts, locate_gvproxy, ports_changed, resolve_ports,
+};
 pub use reconcile::{Action, ApplyResult, apply};
 pub use spec::{
     HealthCheckSpec, MountSpec, NetworkSpec, PortSpec, ResourcesSpec, RestartPolicy, ServiceSpec,