feat(library-udf): add TableFFT function for table model

[dahyvuun]

Description

What is this PR?

Implements TableFFT, a new TableFunction that brings FFT (Fast Fourier Transform) support to the IoTDB table model, as requested in #17939.

Design Decisions

Implements TableFunction interface following the existing RepeatExample pattern in library-udf
Reuses DoubleFFT_1D from JTransforms (already a dependency — no new libs added)
Input values are accumulated in process() and FFT is computed in finish(), since FFT requires the full signal
Outputs n/2 frequency bins (single-sided spectrum for real-valued input)
Supports result parameter (real, imag, abs, angle) consistent with the existing tree model UDTFFFT

Usage

SELECT * FROM TABLE(
table_fft(
TABLE(SELECT time, device_id, value FROM vibration ORDER BY time)
PARTITION BY device_id,
result => 'abs'
)
);

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This PR has:

• been self-reviewed.
  • concurrent read
  • concurrent write
  • concurrent read and write
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods.
• added or updated version, license, or notice information
• added comments explaining the "why" and the intent of the code wherever would not be obvious
  for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold
  for code coverage.
• added integration tests.
• been tested in a test IoTDB cluster.

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Key changed/added classes (or packages if there are too many classes) in this PR

library-udf/src/main/java/org/apache/iotdb/library/frequency/TableFFT.java (new)
library-udf/src/test/java/org/apache/iotdb/library/TableFFTTest.java (new)