feat(ai): integrate local Ollama AI for in-context sentence translation and caching (Task 13)

app/main.py

@@ -29,6 +29,8 @@ from app.dictionary import lookup_term, USER_AGENT, close_http_client
 from app.export import export_csv, export_json, export_anki_tsv, export_markdown
 from app.srs import calculate_sm2, generate_quiz_options, build_activity_heatmap, calculate_cefr_level
 from app.reader import parse_epub, parse_text, parse_pdf, count_words
+from app.ai import translate_sentence_ai, get_ollama_status
+
 
 
 @asynccontextmanager
@@ -153,6 +155,12 @@ class BookProgressRequest(BaseModel):
     position: Optional[float] = None
 
 
+class SentenceTranslateRequest(BaseModel):
+    sentence: str = Field(..., min_length=1)
+    target_word: Optional[str] = ""
+
+
+
 # ---------------------------------------------------------------------------
 # PWA Static Endpoints
 # ---------------------------------------------------------------------------
@@ -321,6 +329,34 @@ async def api_audio_proxy():
     return Response(status_code=204)
 
 
+# ---------------------------------------------------------------------------
+# Local AI Sentence Translation & In-Context Word Lookup
+# ---------------------------------------------------------------------------
+
+@app.post("/api/translate-sentence")
+async def api_translate_sentence(
+    req: SentenceTranslateRequest,
+    user: dict = Depends(require_user)
+):
+    """
+    Translates a sentence using local AI with in-context meaning of the target word.
+    Uses SQLite sentence_translations cache for sub-millisecond retrieval on repeat queries.
+    """
+    clean_s = req.sentence.strip()
+    if not clean_s:
+        raise HTTPException(status_code=400, detail="Sentence cannot be empty")
+    return await translate_sentence_ai(clean_s, req.target_word or "")
+
+
+@app.get("/api/ai/status")
+async def api_ai_status(user: dict = Depends(require_user)):
+    """
+    Returns local AI status and available models.
+    """
+    return await get_ollama_status()
+
+
+
 # ---------------------------------------------------------------------------
 # Collections
 # ---------------------------------------------------------------------------