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>

proto/mcp/v1/mcp.proto

@@ -36,6 +36,13 @@ service McpAgentService {
 
 // --- Service lifecycle ---
 
+message RouteSpec {
+  string name = 1;      // route name (used for $PORT_<NAME>)
+  int32 port = 2;       // external port on mc-proxy
+  string mode = 3;      // "l4" or "l7"
+  string hostname = 4;  // optional public hostname override
+}
+
 message ComponentSpec {
   string name = 1;
   string image = 2;
@@ -45,6 +52,8 @@ message ComponentSpec {
   repeated string ports = 6;
   repeated string volumes = 7;
   repeated string cmd = 8;
+  repeated RouteSpec routes = 9;
+  repeated string env = 10;
 }
 
 message ServiceSpec {