Refactor segment processing with overflow error handling

fix: catch OverflowError in emit_text for very large numbers

Fixes #145

When text contains a very large number (e.g. a long decimal from a binary
hash), misaki's pipeline calls num2words() which raises OverflowError and
crashes the entire job. Wrap the segment iterator in try/except so the
chunk is skipped gracefully with a warning log instead of terminating.

abogen/webui/conversion_runner.py

@@ -1868,6 +1868,7 @@ def run_conversion_job(job: Job) -> None:
                     split_pattern=split_pattern,
                 )
 
+            try:
                 for segment in segment_iter:
                     canceller()
                     graphemes_raw = getattr(segment, "graphemes", "") or ""
@@ -1907,6 +1908,11 @@ def run_conversion_job(job: Job) -> None:
                     if audio_sink:
                         current_time += duration
                         
+            except OverflowError as exc:
+                job.add_log(
+                    f"Skipped chunk — number too large for TTS conversion: {exc}",
+                    level="warning",
+                )
             return local_segments
 
         def append_silence(