feat(ocr): add rotatePages option for automatic page orientation correction

[andreiblaj]

Description of Changes

What was changed

Added a new boolean request parameter rotatePages to the OCR endpoint
(POST /api/v1/misc/ocr-pdf). When set to true, the OCRmyPDF command now
gets --rotate-pages appended, mirroring how the existing deskew / clean
flags are handled.

• ProcessPdfWithOcrRequest — new rotatePages field with a Swagger description.
• OCRController — reads request.isRotatePages(), threads it through the
  command-builder method signature, and appends --rotate-pages when set.

Why

Stirling's OCR is built on OCRmyPDF + Tesseract, which already ships
--rotate-pages. It uses Tesseract OSD (Orientation & Script Detection) to
auto-correct the cardinal orientation (90/180/270) of each page — the standard
fix for scanned documents that arrive sideways or upside-down. Until now there
was no way to trigger it from Stirling:

• rotate-pdf only takes a single angle applied to the whole document (no
  per-page, no auto-detect).
• ocr-pdf exposed deskew, but --deskew only corrects small skew, not
  90/180/270 rotation, so it does not cover this case.

This is a long-standing gap — see #725, where users asked for automatic
orientation/skew correction on scans back in 2024.

Scope

12 lines across 2 files, no new dependencies, no behavior change unless the
caller opts in by sending rotatePages=true.

Verified

Built locally (./gradlew bootJar), ran the server, and called ocr-pdf with
rotatePages=true on a real 20-page scan with mixed 0°/180° pages. The
upside-down pages came out upright, already-upright pages were left untouched,
and the resulting OCR text layer was correct.

Possible follow-up (not in this PR): bare --rotate-pages uses OCRmyPDF's
conservative default --rotate-pages-threshold (15). For noisy/sparse scans a
more aggressive threshold catches more low-confidence pages. That could be
exposed as an additional optional param if maintainers want it — happy to add.

Relates to #725

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Checklist

General

• I have read the Contribution Guidelines
• I have read the Stirling-PDF Developer Guide (if applicable)
• I have read the How to add new languages to Stirling-PDF (if applicable)
• I have performed a self-review of my own code
• My changes generate no new warnings

Documentation

• I have updated relevant docs on Stirling-PDF's doc repo (if functionality has heavily changed)
• I have read the section Add New Translation Tags (for new translation tags only)

Translations (if applicable)

• I ran scripts/counter_translation.py

UI Changes (if applicable)

• Screenshots or videos demonstrating the UI changes are attached (e.g., as comments or direct attachments in the PR)

Testing (if applicable)

• I have run task check to verify linters, typechecks, and tests pass
• I have tested my changes locally. Refer to the Testing Guide for more details.