[hotfix][docs] Fix broken and stale documentation links

[spuru9]

What is the purpose of the change

Refresh user-facing documentation links that broke after source relocations and external site restructuring. All targets were verified reachable (HTTP 200 or file present on master). Applied symmetrically to both the English (docs/content) and Chinese (docs/content.zh) trees.

Brief change log

• gh_link source references (relocated/renamed in flink-runtime):
  • SourceFunction, SinkFunction, Trigger → legacy relocated paths.
  • WithPreCommitTopology / WithPostCommitTopology → renamed SupportsPreCommitTopology / SupportsPostCommitTopology.
• External links:
  • Avro schema-resolution spec, Curator error handling, FLIP-187 title, PyFlink TableEnvironment API doc, Apache Superset Hive guide.
  • Gradle Shadow issue johnrengelman → GradleUp.
  • Debezium reference 1.2/1.3 → stable (MySQL events anchor updated).

Verifying this change

This change is a documentation-only fix without test coverage. Each updated link was checked to resolve to a live target (external URLs returning HTTP 200, gh_link paths present on master).

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

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Generated-by: Claude Code

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CI report:

• 9eb32bf Azure: SUCCESS

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