fix(watcher): handle OCR errors and route failures to output

[rjackr]

• Wrap ocrmypdf execution in try-except to prevent watchdog thread crash on errors (e.g., PriorOcrFoundError)
• Move failed PDFs to the configured output directory instead of leaving them in input
• Append sanitized error reason to filename (truncated at first '-', max 60 chars) while preserving extension
• Apply same YYYY/MM subdirectory logic as successful conversions when output_dir_year_month is enabled
• Add 2-second delay before move and update file timestamp (os.utime) to force immediate SMB/Windows Explorer refresh
• Prevent filename collisions by appending incremental counters (_1, _2, etc.)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.55%. Comparing base (ab6553f) to head (d6c9cf6).
⚠️ Report is 23 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1690   +/-   ##
=======================================
  Coverage   89.55%   89.55%           
=======================================
  Files         134      134           
  Lines       11507    11507           
  Branches     1162     1162           
=======================================
  Hits        10305    10305           
  Misses        871      871           
  Partials      331      331           

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