[KV] Kvscan Server Side

[polyzos]

This PR brings in the server-side implementation for FIP-17, introduced here

#2809

[polyzos]

@wuchong @platinumhamburg @leekeiabstraction @fresh-borzoni PTAL

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds server-side support for KV full-scan sessions (FIP-17), including session lifecycle management, RPC handling, and operator-facing configuration.

Changes:

• Introduces ScannerManager/ScannerContext to manage server-side scan sessions with TTL eviction and concurrency limits.
• Implements TabletService#scanKv to open/continue/close scans and stream batched results.
• Wires scanner cleanup into replica leadership/stop paths and documents new configuration options.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
website/docs/maintenance/configuration.md	Documents new KV scanner TTL/limits configs.
fluss-common/src/main/java/org/apache/fluss/config/ConfigOptions.java	Adds config keys for scanner TTL, eviction interval, and limits.
fluss-server/src/main/java/org/apache/fluss/server/kv/KvTablet.java	Adds openScan to create snapshot-backed scan contexts.
fluss-server/src/main/java/org/apache/fluss/server/kv/scan/ScannerContext.java	New scan session state holder (snapshot/iterator/lease).
fluss-server/src/main/java/org/apache/fluss/server/kv/scan/ScannerManager.java	New session manager with TTL eviction and limit enforcement.
fluss-server/src/main/java/org/apache/fluss/server/tablet/TabletService.java	Implements scanKv RPC using ScannerManager.
fluss-server/src/main/java/org/apache/fluss/server/tablet/TabletServer.java	Instantiates/closes ScannerManager and injects into services.
fluss-server/src/main/java/org/apache/fluss/server/replica/ReplicaManager.java	Closes scanners on leadership change / stopReplica; adds leader KV accessor.
fluss-server/src/main/java/org/apache/fluss/server/replica/Replica.java	Safety-net close of scanners in dropKv().
fluss-server/src/test/java/org/apache/fluss/server/kv/KvTabletTest.java	Adds unit tests for openScan behavior.
fluss-server/src/test/java/org/apache/fluss/server/kv/scan/ScannerManagerTest.java	New tests for session creation, limits, TTL eviction, and shutdown.
fluss-server/src/test/java/org/apache/fluss/server/replica/ReplicaManagerTest.java	Ensures scanners are closed when stopping replicas.

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