feat: audio playback, device selector, i18n fixes

Audio:
- Add AudioPlayback with channel-based cpal output (avoids Send issue)
- Add AudioCapture stub with input device enumeration
- Audio gated behind 'audio' feature flag (needs ALSA/cmake)
- list_output_devices() / list_input_devices() for device selection
- StreamItem::Audio packets forwarded via mpsc channel to cpal callback

i18n:
- Replace all Chinese error messages with English in tsdb
- Replace all Chinese comments/doc strings with English in tscore
- All user-facing strings now in English

Build:
- Add Containerfile.build for containerized builds with audio deps
- CMAKE_POLICY_VERSION_MINIMUM=3.5 workaround for audiopus_sys
- tsclientlib audio feature enabled in workspace (needs cmake)
- 69 tests passing, clippy clean on both audio and non-audio builds

.opencode/Containerfile.build

@@ -0,0 +1,14 @@
+FROM registry.fedoraproject.org/fedora:44
+
+RUN dnf install -y \
+    gcc \
+    pkg-config \
+    cmake \
+    openssl-devel \
+    alsa-lib-devel \
+    && dnf clean all
+
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+ENV PATH="/root/.cargo/bin:${PATH}"
+
+WORKDIR /build