feat: add FastAPI admin dashboard with sync orchestration and test suite

Replace Flask admin with FastAPI app (api/app/) featuring:
- Dashboard with stat cards, sync control, and history
- Mappings CRUD for ARTICOLE_TERTI with CSV import/export
- Article autocomplete from NOM_ARTICOLE
- SKU pre-validation before import
- Sync orchestration: read JSONs -> validate -> import -> log to SQLite
- APScheduler for periodic sync from UI
- File logging to logs/sync_comenzi_YYYYMMDD_HHMMSS.log
- Oracle pool None guard (503 vs 500 on unavailable)

Test suite:
- test_app_basic.py: 30 tests (imports + routes) without Oracle
- test_integration.py: 9 integration tests with Oracle

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

api/app/routers/health.py

@@ -0,0 +1,30 @@
+from fastapi import APIRouter
+from .. import database
+
+router = APIRouter()
+
+@router.get("/health")
+async def health_check():
+    result = {"oracle": "error", "sqlite": "error"}
+
+    # Check Oracle
+    try:
+        if database.pool:
+            with database.pool.acquire() as conn:
+                with conn.cursor() as cur:
+                    cur.execute("SELECT SYSDATE FROM DUAL")
+                    cur.fetchone()
+            result["oracle"] = "ok"
+    except Exception as e:
+        result["oracle"] = str(e)
+
+    # Check SQLite
+    try:
+        db = await database.get_sqlite()
+        await db.execute("SELECT 1")
+        await db.close()
+        result["sqlite"] = "ok"
+    except Exception as e:
+        result["sqlite"] = str(e)
+
+    return result