Phase 0: scheduleragent + mcp-server read-only agent framework

Complete the natural-language scheduler agent's Phase 0 read-only pipeline:

Task #2 (API Key auth mechanism):
- New store/apikey.go: APIKey store (hash, validate, expiry)
- controllers/apikey.go: GenerateAPIKey finally persists + registers RBAC role
- controllers/auth.go: GetUsernameFromToken recognizes xce_ak_ prefix
- middleware/validatehandler.go: isValidToken handles API Key
- config/rbac.yaml: mcp_readonly role (view-only permissions)
- 6 new test files covering unit + integration full-chain

Task #3 (schedulerclient Go library):
- types.go: URM types (URMJob/URMQueue/URMNode/JobStatus/Metrics)
- client.go: read-only Client interface (6 methods)
- httpclient.go: resty-based HTTP implementation
- statusmap.go + _test.go: TDD status mapping (33 tests)

Task #4 (mcp-server binary):
- cmd/main.go: entry, reads XCE_API_URL/XCE_API_KEY, registers 6 MCP tools
- internal/app.go: tool handlers wiring schedulerclient to MCP stdio
- Uses github.com/mark3labs/mcp-go@v0.57.0 for stdio transport

All: go vet clean, go build clean, schedulerclient 33/33 tests pass.
mcp-server binary ~11MB arm64, CGO_ENABLED=0.

Architecture:
  Claude Code --stdio--> mcp-server --HTTP--> apiserver REST API --cgo--> C backend

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

src/frontend/apiserver/middleware/validatehandler.go

@@ -4,6 +4,7 @@ import (
 	"apiserver/common"
 	"apiserver/controllers"
 	"apiserver/models"
+	"apiserver/store"
 	"apiserver/utils"
 	logger "apiserver/utils"
 	"bytes"
@@ -99,6 +100,14 @@ func validateHeader() gin.HandlerFunc {
 }
 
 func isValidToken(tokenString string, IP string) (bool, error) {
+	// Service-account API keys are a distinct credential type from JWTs and
+	// carry no IP binding (they're meant for long-lived automated clients
+	// like the scheduler-agent MCP server, which may not have a stable IP).
+	if strings.HasPrefix(tokenString, models.APIKeyPrefix) {
+		_, ok := store.ValidateAPIKey(tokenString)
+		return ok, nil
+	}
+
 	token, err := jwt.ParseWithClaims(tokenString, &models.JWTClaims{}, func(token *jwt.Token) (interface{}, error) {
 		return []byte(utils.AuthenticationYamlConfig.Token.SecretKey), nil
 	})