feat(translation): backfill sweep + beat + manual trigger (#143 step 3)

tasks/translation.py — translate_posts: picks untranslated posts (title OR
description non-empty), per-post [title, description] batch via the Interpreter
client, stores translations + detected lang + engine_version; passthrough /
already-target posts are marked handled with no stored translation. 503 or a
connection error interrupts (retry next cycle), 400 stops (fix config), per-post
commit keeps progress; wall-clock bounded. Wired into celery (maintenance_long
lane) + a daily beat. No-op unless enabled + base URL set + healthy. GET
/settings/translation/status + POST .../run for the Settings card. Task tests
(stubbed client, monkeypatched session).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CDgx8bQS5YrGRK76v8HUnM

backend/app/api/settings.py

@@ -1,12 +1,23 @@
 """Settings API: import filters, system stats."""
 
+import asyncio
 import secrets
 
 from quart import Blueprint, jsonify, request
-from sqlalchemy import func, select
+from sqlalchemy import func, or_, select
 
 from ..extensions import get_session
-from ..models import AppSetting, Artist, ImageRecord, ImportBatch, ImportSettings, ImportTask, Tag
+from ..models import (
+    AppSetting,
+    Artist,
+    ImageRecord,
+    ImportBatch,
+    ImportSettings,
+    ImportTask,
+    Post,
+    Tag,
+)
+from ..services import interpreter_client as ic
 
 settings_bp = Blueprint("settings", __name__, url_prefix="/api")
 
@@ -285,3 +296,45 @@ async def rotate_extension_api_key():
             row.value = new_value
         await session.commit()
     return jsonify({"key": new_value})
+
+
+# --- Translation (#143): live status + manual "Translate now" --------------
+
+
+@settings_bp.route("/settings/translation/status", methods=["GET"])
+async def translation_status():
+    """For the Settings card: is it on, is a URL set, is the service reachable,
+    and how many posts still await translation. Health runs the sync client in a
+    thread so the event loop isn't blocked."""
+    async with get_session() as session:
+        cfg = await ImportSettings.load(session)
+        untranslated = (await session.execute(
+            select(func.count(Post.id))
+            .where(Post.translated_source_lang.is_(None))
+            .where(or_(
+                Post.post_title.is_not(None), Post.description.is_not(None),
+            ))
+        )).scalar_one()
+    base_url = (cfg.interpreter_base_url or "").strip()
+    healthy = await asyncio.to_thread(ic.health, base_url) if base_url else False
+    return jsonify({
+        "enabled": cfg.translation_enabled,
+        "base_url_set": bool(base_url),
+        "healthy": healthy,
+        "untranslated_count": int(untranslated),
+    })
+
+
+@settings_bp.route("/settings/translation/run", methods=["POST"])
+async def translation_run():
+    """Enqueue the translate sweep now (the Settings 'Translate now' button)."""
+    async with get_session() as session:
+        cfg = await ImportSettings.load(session)
+    if not cfg.translation_enabled or not (cfg.interpreter_base_url or "").strip():
+        return jsonify(
+            {"error": "translation is disabled or no base URL is set"}
+        ), 400
+    from ..tasks.translation import translate_posts
+
+    r = translate_posts.delay()
+    return jsonify({"celery_task_id": r.id}), 202