feat: Add Iceberg REST Catalog server and admin UI (#8175)

* feat: Add Iceberg REST Catalog server

Implement Iceberg REST Catalog API on a separate port (default 8181)
that exposes S3 Tables metadata through the Apache Iceberg REST protocol.

- Add new weed/s3api/iceberg package with REST handlers
- Implement /v1/config endpoint returning catalog configuration
- Implement namespace endpoints (list/create/get/head/delete)
- Implement table endpoints (list/create/load/head/delete/update)
- Add -port.iceberg flag to S3 standalone server (s3.go)
- Add -s3.port.iceberg flag to combined server mode (server.go)
- Add -s3.port.iceberg flag to mini cluster mode (mini.go)
- Support prefix-based routing for multiple catalogs

The Iceberg REST server reuses S3 Tables metadata storage under
/table-buckets and enables DuckDB, Spark, and other Iceberg clients
to connect to SeaweedFS as a catalog.

* feat: Add Iceberg Catalog pages to admin UI

Add admin UI pages to browse Iceberg catalogs, namespaces, and tables.

- Add Iceberg Catalog menu item under Object Store navigation
- Create iceberg_catalog.templ showing catalog overview with REST info
- Create iceberg_namespaces.templ listing namespaces in a catalog
- Create iceberg_tables.templ listing tables in a namespace
- Add handlers and routes in admin_handlers.go
- Add Iceberg data provider methods in s3tables_management.go
- Add Iceberg data types in types.go

The Iceberg Catalog pages provide visibility into the same S3 Tables
data through an Iceberg-centric lens, including REST endpoint examples
for DuckDB and PyIceberg.

* test: Add Iceberg catalog integration tests and reorg s3tables tests

- Reorganize existing s3tables tests to test/s3tables/table-buckets/
- Add new test/s3tables/catalog/ for Iceberg REST catalog tests
- Add TestIcebergConfig to verify /v1/config endpoint
- Add TestIcebergNamespaces to verify namespace listing
- Add TestDuckDBIntegration for DuckDB connectivity (requires Docker)
- Update CI workflow to use new test paths

* fix: Generate proper random UUIDs for Iceberg tables

Address code review feedback:
- Replace placeholder UUID with crypto/rand-based UUID v4 generation
- Add detailed TODO comments for handleUpdateTable stub explaining
  the required atomic metadata swap implementation

* fix: Serve Iceberg on localhost listener when binding to different interface

Address code review feedback: properly serve the localhost listener
when the Iceberg server is bound to a non-localhost interface.

* ci: Add Iceberg catalog integration tests to CI

Add new job to run Iceberg catalog tests in CI, along with:
- Iceberg package build verification
- Iceberg unit tests
- Iceberg go vet checks
- Iceberg format checks

* fix: Address code review feedback for Iceberg implementation

- fix: Replace hardcoded account ID with s3_constants.AccountAdminId in buildTableBucketARN()
- fix: Improve UUID generation error handling with deterministic fallback (timestamp + PID + counter)
- fix: Update handleUpdateTable to return HTTP 501 Not Implemented instead of fake success
- fix: Better error handling in handleNamespaceExists to distinguish 404 from 500 errors
- fix: Use relative URL in template instead of hardcoded localhost:8181
- fix: Add HTTP timeout to test's waitForService function to avoid hangs
- fix: Use dynamic ephemeral ports in integration tests to avoid flaky parallel failures
- fix: Add Iceberg port to final port configuration logging in mini.go

* fix: Address critical issues in Iceberg implementation

- fix: Cache table UUIDs to ensure persistence across LoadTable calls
  The UUID now remains stable for the lifetime of the server session.
  TODO: For production, UUIDs should be persisted in S3 Tables metadata.

- fix: Remove redundant URL-encoded namespace parsing
  mux router already decodes %1F to \x1F before passing to handlers.
  Redundant ReplaceAll call could cause bugs with literal %1F in namespace.

* fix: Improve test robustness and reduce code duplication

- fix: Make DuckDB test more robust by failing on unexpected errors
  Instead of silently logging errors, now explicitly check for expected
  conditions (extension not available) and skip the test appropriately.

- fix: Extract username helper method to reduce duplication
  Created getUsername() helper in AdminHandlers to avoid duplicating
  the username retrieval logic across Iceberg page handlers.

* fix: Add mutex protection to table UUID cache

Protects concurrent access to the tableUUIDs map with sync.RWMutex.
Uses read-lock for fast path when UUID already cached, and write-lock
for generating new UUIDs. Includes double-check pattern to handle race
condition between read-unlock and write-lock.

* style: fix go fmt errors

* feat(iceberg): persist table UUID in S3 Tables metadata

* feat(admin): configure Iceberg port in Admin UI and commands

* refactor: address review comments (flags, tests, handlers)

- command/mini: fix tracking of explicit s3.port.iceberg flag
- command/admin: add explicit -iceberg.port flag
- admin/handlers: reuse getUsername helper
- tests: use 127.0.0.1 for ephemeral ports and os.Stat for file size check

* test: check error from FileStat in verify_gc_empty_test

weed/command/mini.go

@@ -222,6 +222,7 @@ func initMiniS3Flags() {
 	miniS3Options.port = cmdMini.Flag.Int("s3.port", 8333, "s3 server http listen port")
 	miniS3Options.portHttps = cmdMini.Flag.Int("s3.port.https", 0, "s3 server https listen port")
 	miniS3Options.portGrpc = cmdMini.Flag.Int("s3.port.grpc", 0, "s3 server grpc listen port")
+	miniS3Options.portIceberg = cmdMini.Flag.Int("s3.port.iceberg", 8181, "Iceberg REST Catalog server listen port (0 to disable)")
 	miniS3Options.domainName = cmdMini.Flag.String("s3.domainName", "", "suffix of the host name in comma separated list, {bucket}.{domainName}")
 	miniS3Options.allowedOrigins = cmdMini.Flag.String("s3.allowedOrigins", "*", "comma separated list of allowed origins")
 	miniS3Options.tlsPrivateKey = cmdMini.Flag.String("s3.key.file", "", "path to the TLS private key file")
@@ -463,6 +464,14 @@ func ensureAllPortsAvailableOnIP(bindIp string) error {
 			flagName string
 			grpcPtr  *int
 		}{miniS3Options.port, "S3", "s3.port", miniS3Options.portGrpc})
+		if miniS3Options.portIceberg != nil && *miniS3Options.portIceberg > 0 {
+			portConfigs = append(portConfigs, struct {
+				port     *int
+				name     string
+				flagName string
+				grpcPtr  *int
+			}{miniS3Options.portIceberg, "Iceberg", "s3.port.iceberg", nil})
+		}
 	}
 	portConfigs = append(portConfigs, struct {
 		port     *int
@@ -510,9 +519,13 @@ func ensureAllPortsAvailableOnIP(bindIp string) error {
 	initializeGrpcPortsOnIP(bindIp)
 
 	// Log the final port configuration
-	glog.Infof("Final port configuration - Master: %d, Filer: %d, Volume: %d, S3: %d, WebDAV: %d, Admin: %d",
+	icebergPortStr := "disabled"
+	if miniS3Options.portIceberg != nil && *miniS3Options.portIceberg > 0 {
+		icebergPortStr = fmt.Sprintf("%d", *miniS3Options.portIceberg)
+	}
+	glog.Infof("Final port configuration - Master: %d, Filer: %d, Volume: %d, S3: %d, Iceberg: %s, WebDAV: %d, Admin: %d",
 		*miniMasterOptions.port, *miniFilerOptions.port, *miniOptions.v.port,
-		*miniS3Options.port, *miniWebDavOptions.port, *miniAdminOptions.port)
+		*miniS3Options.port, icebergPortStr, *miniWebDavOptions.port, *miniAdminOptions.port)
 
 	// Log gRPC ports too (now finalized)
 	glog.Infof("gRPC port configuration - Master: %d, Filer: %d, Volume: %d, S3: %d, Admin: %d",
@@ -704,7 +717,7 @@ func runMini(cmd *Command, args []string) bool {
 	// Capture which port flags were explicitly passed on CLI BEFORE config file is applied
 	// This is necessary to distinguish user-specified ports from defaults or config file options
 	explicitPortFlags = make(map[string]bool)
-	portFlagNames := []string{"master.port", "filer.port", "volume.port", "s3.port", "webdav.port", "admin.port", "s3.iam.readOnly"}
+	portFlagNames := []string{"master.port", "filer.port", "volume.port", "s3.port", "s3.port.iceberg", "webdav.port", "admin.port", "s3.iam.readOnly"}
 	for _, flagName := range portFlagNames {
 		explicitPortFlags[flagName] = isFlagPassed(flagName)
 	}
@@ -982,7 +995,11 @@ func startMiniAdminWithWorker(allServicesReady chan struct{}) {
 
 	// Start admin server in background
 	go func() {
-		if err := startAdminServer(ctx, miniAdminOptions, *miniEnableAdminUI); err != nil {
+		var icebergPort int
+		if miniS3Options.portIceberg != nil {
+			icebergPort = *miniS3Options.portIceberg
+		}
+		if err := startAdminServer(ctx, miniAdminOptions, *miniEnableAdminUI, icebergPort); err != nil {
 			glog.Errorf("Admin server error: %v", err)
 		}
 	}()