fix(setup,docs): write INSTALL_TESSERACT from setup.ps1, correct the OCR upgrade note

setup.ps1 wrote OCR_ENABLED=true but never INSTALL_TESSERACT=true, so a
Windows user answering yes to the OCR question ended up with OCR on and no
engine in the image; it also claimed tesseract was "shipped in the Docker
image", which this change makes false, and offered OCR for the pre-built
Docker Hub images that cannot include it. Mirror setup.sh: skip the question
for hub images (naming all three settings the DeepSeek path needs), and bake
tesseract in for locally built ones.

The upgrade callout said earlier images always included tesseract. They never
did -- they included docling, and OCR ran on the RapidOCR engine bundled with
it, needing no system package. It also covered only OCR_ENABLED, missing
OCR_ATTACHMENTS_ENABLED, which is a separate switch onto the same native OCR
path.

docs/content/Guides/ocr.mdx

@@ -72,10 +72,12 @@ there, point `OCR_ENGINE=deepseek` at a DeepSeek-OCR endpoint or install
 unaffected).
 
 <Callout type="warning" emoji="⚠️">
-**Upgrading:** earlier images always included tesseract. If your deployment
-runs `OCR_ENABLED=true` with the `tesseract` engine, add
-`INSTALL_TESSERACT=true` to `.env` before rebuilding, or OCR of scanned pages
-stops working after the rebuild.
+**Upgrading:** earlier images always included docling, and OCR ran through the
+RapidOCR engine bundled with it, so no system package was needed. The default
+image now ships neither docling nor tesseract. If your deployment uses the
+`tesseract` engine (the default) with `OCR_ENABLED=true` or
+`OCR_ATTACHMENTS_ENABLED=true`, add `INSTALL_TESSERACT=true` to `.env` before
+rebuilding, or OCR of scanned pages stops working after the rebuild.
 </Callout>
 
 ## Installing the docling engine