chore: merge Rust backend into monorepo

git-subtree-dir: server
git-subtree-mainline: fb6a84d75f
git-subtree-split: 8a88706ff9

server/migrations/0003_async_transcription_jobs.sql

@@ -0,0 +1,8 @@
+ALTER TABLE audio_segments
+  ADD COLUMN transcription_attempts INTEGER NOT NULL DEFAULT 0
+    CHECK (transcription_attempts >= 0),
+  ADD COLUMN processing_started_at TIMESTAMPTZ;
+
+CREATE INDEX audio_segments_processing_queue_idx
+  ON audio_segments (created_at, id)
+  WHERE status = 'processing';