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/services/validation_service.py

@@ -0,0 +1,71 @@
+import logging
+from .. import database
+
+logger = logging.getLogger(__name__)
+
+def validate_skus(skus: set[str]) -> dict:
+    """Validate a set of SKUs against Oracle.
+    Returns: {mapped: set, direct: set, missing: set}
+    - mapped: found in ARTICOLE_TERTI (active)
+    - direct: found in NOM_ARTICOLE by codmat (not in ARTICOLE_TERTI)
+    - missing: not found anywhere
+    """
+    if not skus:
+        return {"mapped": set(), "direct": set(), "missing": set()}
+
+    mapped = set()
+    direct = set()
+    sku_list = list(skus)
+
+    with database.pool.acquire() as conn:
+        with conn.cursor() as cur:
+            # Check in batches of 500
+            for i in range(0, len(sku_list), 500):
+                batch = sku_list[i:i+500]
+                placeholders = ",".join([f":s{j}" for j in range(len(batch))])
+                params = {f"s{j}": sku for j, sku in enumerate(batch)}
+
+                # Check ARTICOLE_TERTI
+                cur.execute(f"""
+                    SELECT DISTINCT sku FROM ARTICOLE_TERTI
+                    WHERE sku IN ({placeholders}) AND activ = 1
+                """, params)
+                for row in cur:
+                    mapped.add(row[0])
+
+                # Check NOM_ARTICOLE for remaining
+                remaining = [s for s in batch if s not in mapped]
+                if remaining:
+                    placeholders2 = ",".join([f":n{j}" for j in range(len(remaining))])
+                    params2 = {f"n{j}": sku for j, sku in enumerate(remaining)}
+                    cur.execute(f"""
+                        SELECT DISTINCT codmat FROM NOM_ARTICOLE
+                        WHERE codmat IN ({placeholders2})
+                    """, params2)
+                    for row in cur:
+                        direct.add(row[0])
+
+    missing = skus - mapped - direct
+
+    logger.info(f"SKU validation: {len(mapped)} mapped, {len(direct)} direct, {len(missing)} missing")
+    return {"mapped": mapped, "direct": direct, "missing": missing}
+
+def classify_orders(orders, validation_result):
+    """Classify orders as importable or skipped based on SKU validation.
+    Returns: (importable_orders, skipped_orders)
+    Each skipped entry is a tuple of (order, list_of_missing_skus).
+    """
+    ok_skus = validation_result["mapped"] | validation_result["direct"]
+    importable = []
+    skipped = []
+
+    for order in orders:
+        order_skus = {item.sku for item in order.items if item.sku}
+        order_missing = order_skus - ok_skus
+
+        if order_missing:
+            skipped.append((order, list(order_missing)))
+        else:
+            importable.append(order)
+
+    return importable, skipped