feat: add storage info to settings page and improve NFS export handling

Backend:
- Add source/used_by/available/error fields to diskUsage in system status
- collectDiskUsage() now reads /proc/mounts, samba shares and NFS exports from DB
- Paths are deduplicated; shared paths list all shares/exports using them
- syscall.Statfs errors surface as available=false with user-facing error
- collectServiceStatus made a method of Server (receiver consistency)

Frontend:
- Settings page now shows two cards: mount points and shared resources
- Each path shows source badge (Sistema/Mount/SMB/NFS), used_by chips, progress bar
- Unavailable paths show amber warning instead of progress bar
- DiskUsage interface updated with new fields
- NFSExport interface updated with structured fields (fsid, async, etc)
- NFS page updated to use new export fields

internal/importer/nfs.go

@@ -3,6 +3,9 @@ package importer
 import (
 	"bufio"
 	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+	"encoding/json"
 	"fmt"
 	"os"
 	"regexp"
@@ -58,11 +61,11 @@ func parseExports(data []byte) ([]db.NFSExport, error) {
 		}
 		export.Clients = validClients
 
-		if export.Options != "" {
-			if err := system.ValidateNFSOptions(export.Options); err != nil {
-				continue
-			}
+		fsid, err := generateImportFSID()
+		if err != nil {
+			continue
 		}
+		export.FSID = fsid
 
 		exports = append(exports, export)
 	}
@@ -141,13 +144,43 @@ func parseExportLine(line string) (db.NFSExport, bool) {
 		options = "rw,sync,no_root_squash"
 	}
 
+	readOnly := strings.Contains(options, "ro")
+	async := strings.Contains(options, "async")
+	rootSquash := !strings.Contains(options, "no_root_squash")
+	subtreeCheck := strings.Contains(options, "subtree_check")
+
+	adv := db.NFSAdvanced{
+		AllSquash: strings.Contains(options, "all_squash"),
+		Secure:    strings.Contains(options, "secure"),
+		WDelay:    strings.Contains(options, "wdelay"),
+		Hide:      strings.Contains(options, "hide"),
+		Crossmnt:  strings.Contains(options, "crossmnt"),
+	}
+	advJSON, _ := json.Marshal(adv)
+
 	return db.NFSExport{
-		Path:    path,
-		Clients: clients,
-		Options: options,
+		Path:         path,
+		Clients:      clients,
+		ReadOnly:     readOnly,
+		Async:        async,
+		RootSquash:   rootSquash,
+		SubtreeCheck: subtreeCheck,
+		Advanced:     string(advJSON),
 	}, true
 }
 
+func generateImportFSID() (int64, error) {
+	var b [4]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		return 0, err
+	}
+	n := binary.BigEndian.Uint32(b[:])
+	if n == 0 {
+		n = 1
+	}
+	return int64(n), nil
+}
+
 func splitExportsClients(s string) []string {
 	var result []string
 	var current []byte