feat(01-01): add RouterConfigSnapshot/Diff/Change ORM models and tests

- Add RouterConfigSnapshot model with Transit ciphertext config_text
  and SHA-256 plaintext hash for deduplication
- Add RouterConfigDiff model for unified diffs between snapshots
- Add RouterConfigChange model for parsed semantic changes
- Export all three from app.models barrel file
- Add unit tests for importability, table names, columns, and types

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

backend/tests/unit/test_config_snapshot_models.py

@@ -0,0 +1,93 @@
+"""Unit tests for RouterConfigSnapshot, RouterConfigDiff, RouterConfigChange models.
+
+Verifies STOR-01 (table/column structure) and STOR-05 (config_text stores ciphertext).
+"""
+
+import uuid
+
+from sqlalchemy import String, Text
+from sqlalchemy.dialects.postgresql import UUID
+
+
+def test_router_config_snapshot_importable():
+    """RouterConfigSnapshot can be imported from app.models."""
+    from app.models import RouterConfigSnapshot
+    assert RouterConfigSnapshot is not None
+
+
+def test_router_config_diff_importable():
+    """RouterConfigDiff can be imported from app.models."""
+    from app.models import RouterConfigDiff
+    assert RouterConfigDiff is not None
+
+
+def test_router_config_change_importable():
+    """RouterConfigChange can be imported from app.models."""
+    from app.models import RouterConfigChange
+    assert RouterConfigChange is not None
+
+
+def test_snapshot_tablename():
+    """RouterConfigSnapshot.__tablename__ is correct."""
+    from app.models import RouterConfigSnapshot
+    assert RouterConfigSnapshot.__tablename__ == "router_config_snapshots"
+
+
+def test_diff_tablename():
+    """RouterConfigDiff.__tablename__ is correct."""
+    from app.models import RouterConfigDiff
+    assert RouterConfigDiff.__tablename__ == "router_config_diffs"
+
+
+def test_change_tablename():
+    """RouterConfigChange.__tablename__ is correct."""
+    from app.models import RouterConfigChange
+    assert RouterConfigChange.__tablename__ == "router_config_changes"
+
+
+def test_snapshot_columns():
+    """RouterConfigSnapshot has all required columns."""
+    from app.models import RouterConfigSnapshot
+    table = RouterConfigSnapshot.__table__
+    expected = {"id", "device_id", "tenant_id", "config_text", "sha256_hash", "collected_at", "created_at"}
+    actual = {c.name for c in table.columns}
+    assert expected.issubset(actual), f"Missing columns: {expected - actual}"
+
+
+def test_diff_columns():
+    """RouterConfigDiff has all required columns."""
+    from app.models import RouterConfigDiff
+    table = RouterConfigDiff.__table__
+    expected = {
+        "id", "device_id", "tenant_id", "old_snapshot_id", "new_snapshot_id",
+        "diff_text", "lines_added", "lines_removed", "created_at",
+    }
+    actual = {c.name for c in table.columns}
+    assert expected.issubset(actual), f"Missing columns: {expected - actual}"
+
+
+def test_change_columns():
+    """RouterConfigChange has all required columns."""
+    from app.models import RouterConfigChange
+    table = RouterConfigChange.__table__
+    expected = {
+        "id", "diff_id", "device_id", "tenant_id",
+        "component", "summary", "raw_line", "created_at",
+    }
+    actual = {c.name for c in table.columns}
+    assert expected.issubset(actual), f"Missing columns: {expected - actual}"
+
+
+def test_snapshot_config_text_is_text_type():
+    """config_text column type is Text (documents Transit ciphertext contract)."""
+    from app.models import RouterConfigSnapshot
+    col = RouterConfigSnapshot.__table__.c.config_text
+    assert isinstance(col.type, Text), f"Expected Text, got {type(col.type)}"
+
+
+def test_snapshot_sha256_hash_is_string_64():
+    """sha256_hash column type is String(64) for plaintext hash deduplication."""
+    from app.models import RouterConfigSnapshot
+    col = RouterConfigSnapshot.__table__.c.sha256_hash
+    assert isinstance(col.type, String), f"Expected String, got {type(col.type)}"
+    assert col.type.length == 64, f"Expected length 64, got {col.type.length}"