feat(ocr): unify config, add manga translation pipeline and context lookahead

- Consolidate module configs into root config.example.json with ocr, vision, and epub sections

- Split LLM OCR workflows into novel_ocr.py (prose) and manga_ocr_llm.py (manga)

- Remove gemini_direct_ocr.py in favor of OpenAI-compatible API endpoints

- Support direct manga translation via --translate, --target-lang, and glossary.md

- Add bidirectional context support: past translations (--context-pages) and lookahead Japanese text (--context-pages-ahead)

- Add per-page JSON audit logging under logs/ and expose OpenAI sampling parameters

config.example.json

@@ -0,0 +1,35 @@
+{
+  "ocr": {
+    "api_key": "PUT_YOUR_API_KEY_HERE",
+    "base_url": "https://your-provider.example.com/v1",
+    "model": "google/gemini-3.7-flash",
+    "temperature": 0,
+    "max_tokens": null,
+    "top_p": null,
+    "reasoning_effort": null
+  },
+  "vision": {
+    "credentials": ""
+  },
+  "epub": {
+    "title": "Your Book Title",
+    "author": "Author Name",
+    "language": "ja",
+    "identifier": "",
+    "publisher": "",
+    "description": "",
+    "date": "",
+    "rights": "",
+    "series": "",
+    "series_index": "",
+    "font_family": "",
+    "vertical": false,
+    "show_chapter_titles": false,
+    "output": "book.epub",
+    "chapter_titles": {
+      "ch00_frontmatter": "",
+      "ch01_chapter00": "Chapter 00",
+      "ch08_backmatter": ""
+    }
+  }
+}