Narrow exception handlers for better diagnostics

Replace broad `except Exception` with specific types (FileNotFoundError,
PermissionError, OSError) so errors are properly categorized in logs.
Users reporting bugs will get actionable messages instead of generic ones.

document-parser/api/documents.py

@@ -91,6 +91,11 @@ async def preview(
         return Response(content=png_bytes, media_type="image/png")
     except ValueError as e:
         raise HTTPException(status_code=404, detail=str(e)) from e
+    except FileNotFoundError as exc:
+        raise HTTPException(status_code=404, detail="PDF file not found on disk") from exc
+    except OSError as exc:
+        logger.exception("I/O error generating preview for %s", doc_id)
+        raise HTTPException(status_code=422, detail="Failed to read PDF file") from exc
     except Exception as exc:
-        logger.exception("Failed to generate preview")
+        logger.exception("Unexpected error generating preview for %s", doc_id)
         raise HTTPException(status_code=422, detail="Failed to generate preview") from exc

document-parser/services/analysis_service.py

@@ -192,5 +192,7 @@ async def _mark_failed(job_id: str, error: str) -> None:
         if job:
             job.mark_failed(error)
             await analysis_repo.update_status(job)
+    except OSError:
+        logger.exception("Database I/O error marking job %s as failed", job_id)
     except Exception:
-        logger.exception("Could not mark job %s as failed", job_id)
+        logger.exception("Unexpected error marking job %s as failed", job_id)

document-parser/services/document_service.py

@@ -79,8 +79,12 @@ async def delete(doc_id: str) -> bool:
             os.unlink(real_path)
         elif os.path.exists(doc.storage_path):
             logger.warning("Refused to delete file outside upload dir: %s", doc.storage_path)
+    except FileNotFoundError:
+        logger.info("File already removed: %s", doc.storage_path)
+    except PermissionError:
+        logger.error("Permission denied deleting file: %s", doc.storage_path)
     except OSError:
-        logger.warning("Could not delete file: %s", doc.storage_path)
+        logger.warning("Could not delete file: %s", doc.storage_path, exc_info=True)
 
     return await document_repo.delete(doc_id)
 
@@ -101,6 +105,9 @@ def _count_pages(file_content: bytes) -> int | None:
     try:
         info = pdfinfo_from_bytes(file_content)
         return info.get("Pages")
-    except Exception:
-        logger.warning("Could not count pages", exc_info=True)
+    except (FileNotFoundError, OSError) as exc:
+        logger.warning("Could not count pages: %s", exc)
+        return None
+    except Exception:
+        logger.warning("Unexpected error counting pages", exc_info=True)
         return None