Add route declarations and automatic port allocation to MCP agent

Service definitions can now declare routes per component instead of
manual port mappings:

  [[components.routes]]
  name = "rest"
  port = 8443
  mode = "l4"

The agent allocates free host ports at deploy time and injects
$PORT/$PORT_<NAME> env vars into containers. Backward compatible:
components with old-style ports= work unchanged.

Changes:
- Proto: RouteSpec message, routes + env fields on ComponentSpec
- Servicedef: RouteDef parsing and validation from TOML
- Registry: component_routes table with host_port tracking
- Runtime: Env field on ContainerSpec, -e flag in BuildRunArgs
- Agent: PortAllocator (random 10000-60000, availability check),
  deploy wiring for route→port mapping and env injection

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/runtime/runtime.go

@@ -16,6 +16,7 @@ type ContainerSpec struct {
 	Ports   []string // "host:container" port mappings
 	Volumes []string // "host:container" volume mounts
 	Cmd     []string // command and arguments
+	Env     []string // environment variables (KEY=VALUE)
 }
 
 // ContainerInfo describes the observed state of a running or stopped container.