feat(sync): sync_phase_failures table for escalation tracking

New table sync_phase_failures(run_id, phase, error_summary, created_at)
with index on (phase, created_at). Minimal schema — no raw payload, no
PII — stores just enough to answer "did phase X fail in the last N
runs?" for the escalation check and the /api/sync/health pill.

Helpers in sqlite_service:
  record_phase_failure(run_id, phase, error_summary)
    INSERT OR REPLACE semantics (one row per run+phase), then prunes
    to the most recent 100 sync_runs. error_summary clipped at 500
    chars defensively.
  get_recent_phase_failures(limit=3) → {phase: count} across the last N
    runs, ordered by started_at desc.

6 unit tests cover creation, counting, pruning, empty state,
idempotency, and limit semantics.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/tests/test_sync_phase_failures.py

@@ -0,0 +1,121 @@
+"""Tests for sync_phase_failures table + helpers."""
+import os
+import sys
+import tempfile
+
+import pytest
+
+pytestmark = pytest.mark.unit
+
+_tmpdir = tempfile.mkdtemp()
+os.environ.setdefault("FORCE_THIN_MODE", "true")
+os.environ.setdefault("SQLITE_DB_PATH", os.path.join(_tmpdir, "test_spf.db"))
+os.environ.setdefault("ORACLE_DSN", "dummy")
+os.environ.setdefault("ORACLE_USER", "dummy")
+os.environ.setdefault("ORACLE_PASSWORD", "dummy")
+os.environ.setdefault("JSON_OUTPUT_DIR", _tmpdir)
+
+_api_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+if _api_dir not in sys.path:
+    sys.path.insert(0, _api_dir)
+
+from app import database
+from app.services import sqlite_service
+
+
+@pytest.fixture(autouse=True)
+async def _reset():
+    database.init_sqlite()
+    db = await sqlite_service.get_sqlite()
+    try:
+        await db.execute("DELETE FROM sync_phase_failures")
+        await db.execute("DELETE FROM sync_runs")
+        await db.commit()
+    finally:
+        await db.close()
+    yield
+
+
+async def _make_run(run_id: str, offset_seconds: int = 0):
+    db = await sqlite_service.get_sqlite()
+    try:
+        await db.execute(
+            "INSERT INTO sync_runs (run_id, started_at, status) VALUES (?, datetime('now', ?), 'running')",
+            (run_id, f"{offset_seconds} seconds"),
+        )
+        await db.commit()
+    finally:
+        await db.close()
+
+
+async def test_table_created_on_init():
+    db = await sqlite_service.get_sqlite()
+    try:
+        cur = await db.execute(
+            "SELECT name FROM sqlite_master WHERE type='table' AND name='sync_phase_failures'"
+        )
+        row = await cur.fetchone()
+        assert row is not None
+    finally:
+        await db.close()
+
+
+async def test_record_and_read_phase_failures():
+    await _make_run("run-1")
+    await _make_run("run-2", offset_seconds=1)
+    await sqlite_service.record_phase_failure("run-1", "price_sync", "IntegrityError: X")
+    await sqlite_service.record_phase_failure("run-2", "price_sync", "IntegrityError: Y")
+
+    counts = await sqlite_service.get_recent_phase_failures(limit=3)
+    assert counts.get("price_sync") == 2
+
+
+async def test_get_recent_limit_respected():
+    # 5 runs, each with a price_sync failure. Limit=3 should only count the latest 3.
+    for i in range(5):
+        run_id = f"run-{i}"
+        await _make_run(run_id, offset_seconds=i)
+        await sqlite_service.record_phase_failure(run_id, "price_sync", "fail")
+
+    counts = await sqlite_service.get_recent_phase_failures(limit=3)
+    assert counts["price_sync"] == 3
+
+
+async def test_record_prunes_to_100_runs():
+    # Insert 105 runs each with a failure → table should end at <=100 rows after prune.
+    for i in range(105):
+        run_id = f"R{i:03d}"
+        await _make_run(run_id, offset_seconds=i)
+        await sqlite_service.record_phase_failure(run_id, "import_loop", "x")
+
+    db = await sqlite_service.get_sqlite()
+    try:
+        cur = await db.execute("SELECT COUNT(*) FROM sync_phase_failures")
+        (total,) = await cur.fetchone()
+    finally:
+        await db.close()
+    assert total <= 100
+
+
+async def test_empty_phase_failures_returns_empty_dict():
+    counts = await sqlite_service.get_recent_phase_failures(limit=3)
+    assert counts == {}
+
+
+async def test_record_phase_failure_idempotent_per_run_phase():
+    """PRIMARY KEY (run_id, phase) → second insert same run+phase updates in place."""
+    await _make_run("run-idem")
+    await sqlite_service.record_phase_failure("run-idem", "invoice_check", "first")
+    await sqlite_service.record_phase_failure("run-idem", "invoice_check", "second")
+
+    db = await sqlite_service.get_sqlite()
+    try:
+        cur = await db.execute(
+            "SELECT COUNT(*), MAX(error_summary) FROM sync_phase_failures WHERE run_id=? AND phase=?",
+            ("run-idem", "invoice_check"),
+        )
+        (count, latest) = await cur.fetchone()
+    finally:
+        await db.close()
+    assert count == 1
+    assert latest == "second"