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/registry/db.go

@@ -127,4 +127,19 @@ var migrations = []string{
 	CREATE INDEX IF NOT EXISTS idx_events_component_time
 		ON events(service, component, timestamp);
 	`,
+
+	// Migration 2: component routes
+	`
+	CREATE TABLE IF NOT EXISTS component_routes (
+		service   TEXT NOT NULL,
+		component TEXT NOT NULL,
+		name      TEXT NOT NULL,
+		port      INTEGER NOT NULL,
+		mode      TEXT NOT NULL DEFAULT 'l4',
+		hostname  TEXT NOT NULL DEFAULT '',
+		host_port INTEGER NOT NULL DEFAULT 0,
+		PRIMARY KEY (service, component, name),
+		FOREIGN KEY (service, component) REFERENCES components(service, name) ON DELETE CASCADE
+	);
+	`,
 }