fix(lint): resolve all ruff lint errors

Add ruff config to exclude alembic E402, SQLAlchemy F821, and pre-existing
E501 line-length issues. Auto-fix 69 unused imports and 2 f-strings without
placeholders. Manually fix 8 unused variables. Apply ruff format to 127 files.

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

backend/tests/unit/test_config_snapshot_models.py

@@ -3,53 +3,65 @@
 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"}
+    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}"
 
@@ -57,10 +69,18 @@ def test_snapshot_columns():
 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",
+        "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}"
@@ -69,10 +89,17 @@ def test_diff_columns():
 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",
+        "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}"
@@ -81,6 +108,7 @@ def test_change_columns():
 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)}"
 
@@ -88,6 +116,7 @@ def test_snapshot_config_text_is_text_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}"