feat: media_async + media_index modules, media_files table, tests

- media_async: thread-per-task async engine with primitives (sha256, sign, copy, uuid, file_size)
- media_index: media_files DB table with register_async for indexing chunks
- chat_msg: async media submission via register_async, simplified chat_msg_submit fields
- voice_recorder/attachment_sender: write single file (no chunk splitting on caller side)
- inputbar/messagelist: updated to new simplified submit interface
- test_media_async: 4-thread stress test (200K ops / 2 sec, 0 errors)
- test_media_index: 9 cases covering commit edge cases + async flow
- build: Makefile.am, CMakeLists.txt, utun_sources.cmake updated

lib/audio_compressor.c

@@ -78,14 +78,14 @@ void audio_compressor_configure(struct audio_compressor* ac, const audio_compres
     ac->block_samples = ac->cfg.sample_rate * ac->cfg.block_duration_ms / 1000 * ac->cfg.channels;
     ac->lookback_blocks  = ac->cfg.lookback_ms / ac->cfg.block_duration_ms;
     ac->lookahead_blocks = ac->cfg.lookahead_ms / ac->cfg.block_duration_ms;
-    ac->rise_factor_per_block = powf(ac->cfg.rise_rate_per_500ms, (float)ac->cfg.block_duration_ms / 500.0f);
+    ac->rise_factor_per_block = powf(ac->cfg.rise_rate_per_sec, (float)ac->cfg.block_duration_ms / 1000.0f);
     ac->max_gain = powf(10.0f, ac->cfg.max_gain_db / 20.0f);
 
     DEBUG_INFO(DEBUG_CATEGORY_GENERAL,
-        "audio_compressor_configure: rate=%d ch=%d block=%dms lookback=%dms lookahead=%dms maxGain=%.0fdB riseRate=%.1f/500ms target=%.0fdBFS",
+        "audio_compressor_configure: rate=%d ch=%d block=%dms lookback=%dms lookahead=%dms maxGain=%.0fdB riseRate=%.1f/sec target=%.0fdBFS",
         ac->cfg.sample_rate, ac->cfg.channels, ac->cfg.block_duration_ms,
         ac->cfg.lookback_ms, ac->cfg.lookahead_ms, ac->cfg.max_gain_db,
-        ac->cfg.rise_rate_per_500ms, 20.0f * log10f(ac->cfg.target_level));
+        ac->cfg.rise_rate_per_sec, 20.0f * log10f(ac->cfg.target_level));
 }
 
 void audio_compressor_reset(struct audio_compressor* ac) {

lib/audio_compressor.h

@@ -17,7 +17,7 @@ typedef struct {
     int lookback_ms;
     int lookahead_ms;
     float max_gain_db;
-    float rise_rate_per_500ms;
+    float rise_rate_per_sec;
     float target_level;
 } audio_compressor_config_t;