[feat][trace] support trace table sharding by workspace

[cuichen01]

• Add SupportShard/ShardList to TableCfg for per-TTL shard configuration
• Add TenantShardConfig type and GetTenantShardConfig interface method
• Read path: expand shard tables in getQueryTenantTables (full double-read)
• Write path: route InsertSpans/InsertAnnotations to correct shard by workspace
• Group exporter writes by (TTL, WorkspaceID) pair

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[codecov]

Codecov Report

❌ Patch coverage is 45.45455% with 36 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
backend/modules/observability/infra/repo/trace.go	34.04%	29 Missing and 2 partials ⚠️
...ackend/modules/observability/infra/config/trace.go	0.00%	5 Missing ⚠️

❌ Your patch check has failed because the patch coverage (45.45%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

@@           Coverage Diff           @@
##             main     #636   +/-   ##
=======================================
  Coverage        ?   78.41%           
=======================================
  Files           ?      694           
  Lines           ?    85522           
  Branches        ?        0           
=======================================
  Hits            ?    67065           
  Misses          ?    14529           
  Partials        ?     3928           

Flag	Coverage Δ
unittests	78.41% <45.45%> (?)

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Files with missing lines	Coverage Δ
...es/observability/domain/component/config/config.go	39.28% <ø> (ø)
...exporter/clickhouseexporter/clickhouse_exporter.go	100.00% <100.00%> (ø)
...ackend/modules/observability/infra/config/trace.go	63.27% <0.00%> (ø)
backend/modules/observability/infra/repo/trace.go	82.17% <34.04%> (ø)

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