Remove progress throttle so every segment emits a progress update

Previously, progress messages were only sent every 5th segment due to
a `segment_count % 5` guard. This made the UI feel unresponsive for
short recordings with few segments. Now every segment emits a progress
update with a more descriptive message including the segment number
and audio percentage.

Adds a test verifying that all 8 mock segments produce progress
messages, not just every 5th.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

python/voice_to_notes/services/transcribe.py

@@ -145,16 +145,14 @@ class TranscribeService:
                 )
             )
 
-            # Send progress every few segments
-            if segment_count % 5 == 0:
-                write_message(
-                    progress_message(
-                        request_id,
-                        progress_pct,
-                        "transcribing",
-                        f"Processed {segment_count} segments...",
-                    )
+            write_message(
+                progress_message(
+                    request_id,
+                    progress_pct,
+                    "transcribing",
+                    f"Transcribing segment {segment_count} ({progress_pct}% of audio)...",
                 )
+            )
 
         elapsed = time.time() - start_time
         print(