Transcribe in batches instead of one file per whisper run

Every whisper.cpp invocation loads the model from scratch, which for a large
model takes longer than recognising a few seconds of speech. Running it once per
file meant that across seventeen thousand recordings the loading would dominate
the work entirely. Files now go in batches of sixteen — 40 files took 3 runs
instead of 40 in a stub test, with each file still getting its own result.

A batch has to be one language, since -l applies to the whole invocation, so work
is grouped by the language derived from the wavs/<code>/ path. Results come back
as files next to the inputs (-otxt) rather than on stdout, because with several
files in one run stdout cannot be split per file. Cancellation now lands between
batches rather than between files, which at sixteen files is close enough.

Thread count is left at whisper's own default and exposed as
catalog.whisper.threads: raising it buys speed at the cost of heat, and on a
fanless machine that turns into throttling anyway.

Docker: whisper.cpp bumped to v1.9.2 to match what Homebrew installs. The library
naming changed there — versioned sonames like libggml.so.0 — and the copy pattern
had to widen to match, otherwise the binary could not start.

Verified with a stub in place of whisper-cli, on the host and inside the
container: batching holds, each file gets its own text, and the temp directory
works as uid 10001. Nothing was left in the transcript table.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Dockerfile

@@ -24,13 +24,13 @@ RUN ./gradlew --no-daemon installDist \
 FROM debian:bookworm-slim AS whisper
 RUN apt-get update \
  && apt-get install -y --no-install-recommends git cmake build-essential ca-certificates \
- && git clone --depth 1 --branch v1.7.4 https://github.com/ggerganov/whisper.cpp /src \
+ && git clone --depth 1 --branch v1.9.2 https://github.com/ggerganov/whisper.cpp /src \
  && cmake -S /src -B /src/build -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON \
       -DGGML_NATIVE=OFF -DWHISPER_BUILD_TESTS=OFF -DWHISPER_BUILD_EXAMPLES=ON \
  && cmake --build /src/build --target whisper-cli -j "$(nproc)" \
  && mkdir -p /out/bin /out/lib \
  && cp /src/build/bin/whisper-cli /out/bin/ \
- && find /src/build \( -name 'libwhisper.so*' -o -name 'libggml*.so' \) \
+ && find /src/build \( -name 'libwhisper.so*' -o -name 'libggml*.so*' \) \
       -exec cp -P {} /out/lib/ \; \
  && rm -rf /var/lib/apt/lists/* /src