feat: Add individual start/stop control for streaming, recording, and replay buffer

[hanatyan128]

Summary

• Add per-output individual start/stop methods (startStreamingIndividual, startRecordingIndividual, startReplayBufferIndividual and their stop counterparts)
• Add INTERLOCK_TYPE_INDIVIDUAL mode that maps OBS streaming/recording/replay buffer states to their Branch Output counterparts independently
• Add OutputCell widget to status dock with per-output enable/disable checkbox (works in all interlock modes), preserving folder-open click for recording/replay buffer rows
• Refactor ensureInfrastructure() / releaseInfrastructureIfIdle() to separate shared resource lifecycle from individual output lifecycle, allowing outputs to start/stop independently while sharing the same view, encoders, and audio context

Thread Safety Improvements

• Add audioMutex to protect audio capture pointers in audioFilterCallback against concurrent release in releaseInfrastructureIfIdle
• Switch all three mutexes (pluginMutex, outputMutex, audioMutex) to PTHREAD_MUTEX_RECURSIVE via OBS's pthread_mutex_init_recursive(), eliminating the need for separate *Locked() method variants
• Make outputStarting (std::atomic<bool>) and reconnectAttemptingAt (std::atomic<uint64_t>) atomic to eliminate data races from OBS signal callbacks that write these fields on core threads
• Add default member initializers to BranchOutputStreamingContext and change createSreamingOutput() to populate streamings[] in-place, removing move constructor/assignment requirements
• Add early-return guard in startOutput() when all user-enabled flags are false, preventing infrastructure rebuild loops in ALWAYS_ON mode
• Unify lock ordering in stopOutputGracefully() to match pluginMutex -> outputMutex convention used elsewhere

User-Facing Changes

• Per-output user intent flags (streamingUserEnabled[], recordingUserEnabled, replayBufferUserEnabled) are persisted via saveCallback with backward-compatible migration from the legacy streaming_output_enabled key
• New locale keys added to all 10 locale files: Individual, StreamingToggleTooltip, RecordingToggleTooltip, ReplayBufferToggleTooltip

Files Changed (18 files, +1211 / -490)

• src/plugin-main.cpp/hpp — Core logic: infrastructure separation, recursive mutexes, individual start/stop orchestration in onIntervalTimerTimeout, save/load of user intent flags
• src/plugin-streaming.cpp — startStreamingIndividual, stopStreamingIndividual, startSingleStreamingIndividual, stopSingleStreamingIndividual, atomic fields, in-place output creation
• src/plugin-stream-recording.cpp — startRecordingIndividual, stopRecordingIndividual
• src/plugin-replay-buffer.cpp — startReplayBufferIndividual, stopReplayBufferIndividual
• src/plugin-ui.cpp — INTERLOCK_TYPE_INDIVIDUAL option in interlock dropdown
• src/UI/output-status-dock.cpp/hpp — OutputCell class (unified from former RecordingOutputCell/ReplayBufferOutputCell), per-output checkbox sync
• data/locale/*.ini — New locale keys for all 10 languages

Test Plan

• Verify INTERLOCK_TYPE_INDIVIDUAL mode: OBS streaming start → only Branch Output streaming starts; OBS recording start → only Branch Output recording starts
• Verify per-output checkboxes in status dock work in all interlock modes (ALWAYS_ON, Streaming, Recording, etc.)
• Verify unchecking all outputs in ALWAYS_ON mode does not cause infrastructure rebuild loop
• Verify enable/disable filter (eye icon) does not crash with individual stopping in progress
• Verify OBS shutdown does not crash with active individual outputs
• Verify scene collection switch does not crash
• Verify no memory leaks on OBS shutdown
• Test on Windows x64 (primary), macOS and Linux if possible

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