feat(analysis): add in-process ocrs OCR backend

Add a CPU-only, English-first OCR engine (the `ocrs` crate on the `rten`
runtime) as an alternative to the local-LLM "vision" backend, which ran
too slowly on the target Raspberry Pi 5.

- `ANALYSIS_BACKEND` (default `ocr`) selects the engine; `vision` keeps the
  existing LLM path. Deploy-time, env-only — not admin-tunable.
- `analysis::ocr` adds an `OcrEngine` trait (testable seam), the `OcrsEngine`
  impl (models loaded once, inference on the blocking pool), and an
  `OcrAnalyzeDispatcher` that plugs into the existing `AnalyzeDispatcher`
  seam and reuses `persist_analysis`, so OCR text lands in `page_ocr_text`
  and the `search_doc` tsvector exactly as the vision path produces them.
- The backend image bakes the two `.rten` models into /models, where
  `OCRS_DETECTION_MODEL` / `OCRS_RECOGNITION_MODEL` default.

Because `/v1/me/page-search` ranks on `search_doc`, OCR text search works
the moment pages are processed. Auto-tagging, scene description and NSFW
flags remain the vision backend's job (deferred).

Bumps to 0.90.0 (minor) in both manifests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/Dockerfile

@@ -58,6 +58,20 @@ WORKDIR /app
 COPY --from=builder /app/target/release/mangalord /usr/local/bin/mangalord
 COPY --from=builder /app/migrations /app/migrations
 
+# OCR models for the default `ANALYSIS_BACKEND=ocr` (ocrs) engine. The two
+# `.rten` files are pulled at build time into /models, where the runtime's
+# `OCRS_DETECTION_MODEL` / `OCRS_RECOGNITION_MODEL` defaults point. They're a
+# few MB each and pure data (no native code), so they bake cleanly into the
+# image and need no manual setup on the Pi. Set INSTALL_OCR_MODELS=false to
+# skip (e.g. for a vision-only deploy that never runs ocrs).
+ARG INSTALL_OCR_MODELS=true
+ARG OCRS_MODEL_BASE_URL=https://ocrs-models.s3-accelerate.amazonaws.com
+RUN if [ "$INSTALL_OCR_MODELS" = "true" ]; then \
+      mkdir -p /models \
+      && curl -fsSL "${OCRS_MODEL_BASE_URL}/text-detection.rten"   -o /models/text-detection.rten \
+      && curl -fsSL "${OCRS_MODEL_BASE_URL}/text-recognition.rten" -o /models/text-recognition.rten; \
+    fi
+
 ENV STORAGE_DIR=/var/lib/mangalord/storage
 # Pre-create the storage dir so the entrypoint doesn't need to
 # mkdir-as-root and so the named volume mount inherits the right