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>

.env.example

@@ -277,6 +277,19 @@ CRAWLER_TZ=UTC
 # ANALYSIS_ENABLED   Turn the worker on at first boot. Toggleable live in
 #                    the dashboard. Default `false`.
 ANALYSIS_ENABLED=false
+# ANALYSIS_BACKEND  Which engine the worker runs. env-ONLY (deploy-time).
+#                   `ocr` (default) = the in-process ocrs engine: fast,
+#                   CPU-only, text-only, ideal for a Pi. `vision` = the local
+#                   LLM at ANALYSIS_VISION_URL (full OCR + tags + scene +
+#                   safety, but heavy). The ANALYSIS_VISION_* / ANALYSIS_API_KEY
+#                   knobs below only apply to `vision`.
+ANALYSIS_BACKEND=ocr
+# OCRS_DETECTION_MODEL / OCRS_RECOGNITION_MODEL  Paths to the ocrs `.rten`
+#   text-detection / -recognition models (only read when ANALYSIS_BACKEND=ocr).
+#   The backend image bakes both into /models, so the defaults work unchanged;
+#   override only to point at custom-trained models.
+OCRS_DETECTION_MODEL=/models/text-detection.rten
+OCRS_RECOGNITION_MODEL=/models/text-recognition.rten
 # ANALYSIS_VISION_URL  /v1/chat/completions endpoint. Required when enabled.
 #                      For the bundled vision container, use
 #                      http://mangalord-vision:8000/v1/chat/completions.