fix: replace TotalShardsCount with MaxShardCount in critical data structures

Critical fixes for buffer allocations and loops that must support
custom EC ratios up to 32 shards:

Data Structures:
- store_ec.go:354: Buffer allocation for shard recovery (bufs array)
- topology_ec.go:14: EcShardLocations.Locations fixed array size
- command_ec_rebuild.go:268: EC shard map allocation
- command_ec_common.go:626: Shard-to-locations map allocation

Shard Discovery Loops:
- ec_task.go:378: Loop to find generated shard files
- ec_shard_management.go: All 8 loops that check/count EC shards

These changes are critical because:
1. Buffer allocations sized to 14 would cause index-out-of-bounds panics
   when accessing shards 14-31
2. Fixed arrays sized to 14 would truncate shard location data
3. Loops limited to 0-13 would never discover/manage shards 14-31

Note: command_ec_encode.go:208 intentionally NOT changed - it creates
shard IDs to mount after encoding. In Phase 1 we always generate 14
shards, so this remains TotalShardsCount and will be made dynamic in
Phase 2 based on actual EC context.

Without these fixes, custom EC ratios > 14 total shards would cause:
- Runtime panics (array index out of bounds)
- Data loss (shards 14-31 never discovered/tracked)
- Incomplete shard management (missing shards not detected)

weed/admin/dash/ec_shard_management.go

@@ -68,7 +68,7 @@ func (s *AdminServer) GetClusterEcShards(page int, pageSize int, sortBy string,
 
 								// Create individual shard entries for each shard this server has
 								shardBits := ecShardInfo.EcIndexBits
-								for shardId := 0; shardId < erasure_coding.TotalShardsCount; shardId++ {
+								for shardId := 0; shardId < erasure_coding.MaxShardCount; shardId++ {
 									if (shardBits & (1 << uint(shardId))) != 0 {
 										// Mark this shard as present for this volume
 										volumeShardsMap[volumeId][shardId] = true
@@ -112,13 +112,13 @@ func (s *AdminServer) GetClusterEcShards(page int, pageSize int, sortBy string,
 		shardCount := len(shardsPresent)
 
 		// Find which shards are missing for this volume across ALL servers
-		for shardId := 0; shardId < erasure_coding.TotalShardsCount; shardId++ {
+		for shardId := 0; shardId < erasure_coding.MaxShardCount; shardId++ {
 			if !shardsPresent[shardId] {
 				missingShards = append(missingShards, shardId)
 			}
 		}
 
-		isComplete := (shardCount == erasure_coding.TotalShardsCount)
+		isComplete := (shardCount == erasure_coding.MaxShardCount)
 		volumeCompleteness[volumeId] = isComplete
 		volumeMissingShards[volumeId] = missingShards
 
@@ -332,7 +332,7 @@ func (s *AdminServer) GetClusterEcVolumes(page int, pageSize int, sortBy string,
 
 								// Process each shard this server has for this volume
 								shardBits := ecShardInfo.EcIndexBits
-								for shardId := 0; shardId < erasure_coding.TotalShardsCount; shardId++ {
+								for shardId := 0; shardId < erasure_coding.MaxShardCount; shardId++ {
 									if (shardBits & (1 << uint(shardId))) != 0 {
 										// Record shard location
 										volume.ShardLocations[shardId] = node.Id
@@ -394,7 +394,7 @@ func (s *AdminServer) GetClusterEcVolumes(page int, pageSize int, sortBy string,
 
 		// Find missing shards
 		var missingShards []int
-		for shardId := 0; shardId < erasure_coding.TotalShardsCount; shardId++ {
+		for shardId := 0; shardId < erasure_coding.MaxShardCount; shardId++ {
 			if _, exists := volume.ShardLocations[shardId]; !exists {
 				missingShards = append(missingShards, shardId)
 			}
@@ -523,7 +523,7 @@ func sortEcVolumes(volumes []EcVolumeWithShards, sortBy string, sortOrder string
 // getShardCount returns the number of shards represented by the bitmap
 func getShardCount(ecIndexBits uint32) int {
 	count := 0
-	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+	for i := 0; i < erasure_coding.MaxShardCount; i++ {
 		if (ecIndexBits & (1 << uint(i))) != 0 {
 			count++
 		}
@@ -534,7 +534,7 @@ func getShardCount(ecIndexBits uint32) int {
 // getMissingShards returns a slice of missing shard IDs for a volume
 func getMissingShards(ecIndexBits uint32) []int {
 	var missing []int
-	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+	for i := 0; i < erasure_coding.MaxShardCount; i++ {
 		if (ecIndexBits & (1 << uint(i))) == 0 {
 			missing = append(missing, i)
 		}
@@ -614,7 +614,7 @@ func (s *AdminServer) GetEcVolumeDetails(volumeID uint32, sortBy string, sortOrd
 
 									// Create individual shard entries for each shard this server has
 									shardBits := ecShardInfo.EcIndexBits
-									for shardId := 0; shardId < erasure_coding.TotalShardsCount; shardId++ {
+									for shardId := 0; shardId < erasure_coding.MaxShardCount; shardId++ {
 										if (shardBits & (1 << uint(shardId))) != 0 {
 											ecShard := EcShardWithInfo{
 												VolumeID:     ecShardInfo.Id,
@@ -698,11 +698,11 @@ func (s *AdminServer) GetEcVolumeDetails(volumeID uint32, sortBy string, sortOrd
 	}
 
 	totalUniqueShards := len(foundShards)
-	isComplete := (totalUniqueShards == erasure_coding.TotalShardsCount)
+	isComplete := (totalUniqueShards == erasure_coding.MaxShardCount)
 
 	// Calculate missing shards
 	var missingShards []int
-	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+	for i := 0; i < erasure_coding.MaxShardCount; i++ {
 		if !foundShards[i] {
 			missingShards = append(missingShards, i)
 		}

weed/shell/command_ec_common.go

@@ -622,7 +622,8 @@ func (ecb *ecBalancer) deleteDuplicatedEcShards(collection string) error {
 
 func (ecb *ecBalancer) doDeduplicateEcShards(collection string, vid needle.VolumeId, locations []*EcNode) error {
 	// check whether this volume has ecNodes that are over average
-	shardToLocations := make([][]*EcNode, erasure_coding.TotalShardsCount)
+	// Use MaxShardCount (32) to support custom EC ratios
+	shardToLocations := make([][]*EcNode, erasure_coding.MaxShardCount)
 	for _, ecNode := range locations {
 		shardBits := findEcVolumeShards(ecNode, vid)
 		for _, shardId := range shardBits.ShardIds() {

weed/shell/command_ec_rebuild.go

@@ -261,12 +261,13 @@ type EcShardLocations [][]*EcNode
 func (ecShardMap EcShardMap) registerEcNode(ecNode *EcNode, collection string) {
 	for _, diskInfo := range ecNode.info.DiskInfos {
 		for _, shardInfo := range diskInfo.EcShardInfos {
-			if shardInfo.Collection == collection {
-				existing, found := ecShardMap[needle.VolumeId(shardInfo.Id)]
-				if !found {
-					existing = make([][]*EcNode, erasure_coding.TotalShardsCount)
-					ecShardMap[needle.VolumeId(shardInfo.Id)] = existing
-				}
+		if shardInfo.Collection == collection {
+			existing, found := ecShardMap[needle.VolumeId(shardInfo.Id)]
+			if !found {
+				// Use MaxShardCount (32) to support custom EC ratios
+				existing = make([][]*EcNode, erasure_coding.MaxShardCount)
+				ecShardMap[needle.VolumeId(shardInfo.Id)] = existing
+			}
 				for _, shardId := range erasure_coding.ShardBits(shardInfo.EcIndexBits).ShardIds() {
 					existing[shardId] = append(existing[shardId], ecNode)
 				}

weed/storage/store_ec.go

@@ -350,7 +350,8 @@ func (s *Store) recoverOneRemoteEcShardInterval(needleId types.NeedleId, ecVolum
 		return 0, false, fmt.Errorf("failed to create encoder: %w", err)
 	}
 
-	bufs := make([][]byte, erasure_coding.TotalShardsCount)
+	// Use MaxShardCount to support custom EC ratios up to 32 shards
+	bufs := make([][]byte, erasure_coding.MaxShardCount)
 
 	var wg sync.WaitGroup
 	ecVolume.ShardLocationsLock.RLock()

weed/topology/topology_ec.go

@@ -10,7 +10,8 @@ import (
 
 type EcShardLocations struct {
 	Collection string
-	Locations  [erasure_coding.TotalShardsCount][]*DataNode
+	// Use MaxShardCount (32) to support custom EC ratios
+	Locations  [erasure_coding.MaxShardCount][]*DataNode
 }
 
 func (t *Topology) SyncDataNodeEcShards(shardInfos []*master_pb.VolumeEcShardInformationMessage, dn *DataNode) (newShards, deletedShards []*erasure_coding.EcVolumeInfo) {

weed/worker/tasks/erasure_coding/ec_task.go

@@ -374,7 +374,8 @@ func (t *ErasureCodingTask) generateEcShardsLocally(localFiles map[string]string
 	var generatedShards []string
 	var totalShardSize int64
 
-	for i := 0; i < erasure_coding.TotalShardsCount; i++ {
+	// Check up to MaxShardCount (32) to support custom EC ratios
+	for i := 0; i < erasure_coding.MaxShardCount; i++ {
 		shardFile := fmt.Sprintf("%s.ec%02d", baseName, i)
 		if info, err := os.Stat(shardFile); err == nil {
 			shardKey := fmt.Sprintf("ec%02d", i)