Fix all 98 ruff lint errors across codebase

- Remove unused imports (app.py, stego_routes.py, killswitch.py, etc.)
- Sort import blocks (I001)
- Add missing os import in stego_routes.py (F821)
- Rename shadowed Click commands to avoid F811 (status→chain_status, show→chain_show)
- Rename uppercase locals R→earth_r, _HAS_QRCODE_READ→_has_qrcode_read (N806)
- Suppress false-positive F821 for get_username (closure scope)
- Use datetime.UTC alias (UP017)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import os
 from pathlib import Path
 
 import pytest

tests/test_chain.py

@@ -203,9 +203,7 @@ def test_metadata_in_chain(chain_dir: Path, private_key: Ed25519PrivateKey):
     """Metadata is preserved through append and retrieval."""
     store = ChainStore(chain_dir)
     meta = {"caption": "evidence photo", "backfilled": True}
-    record = store.append(
-        hashlib.sha256(b"test").digest(), "test/plain", private_key, metadata=meta
-    )
+    store.append(hashlib.sha256(b"test").digest(), "test/plain", private_key, metadata=meta)
 
     loaded = store.get(0)
     assert loaded.metadata == meta
@@ -232,14 +230,16 @@ def test_verify_chain_detects_signer_change(chain_dir: Path):
 
     # Manually bypass normal append to inject a record signed by key2.
     # We need to build the record with correct prev_hash but wrong signer.
-    import struct
     import fcntl
-    from soosef.federation.serialization import serialize_record
-    from soosef.federation.models import AttestationChainRecord
-    from soosef.federation.entropy import collect_entropy_witnesses
-    from uuid_utils import uuid7
+    import struct
+
     from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat
+    from uuid_utils import uuid7
+
+    from soosef.federation.entropy import collect_entropy_witnesses
+    from soosef.federation.models import AttestationChainRecord
     from soosef.federation.serialization import canonical_bytes as cb
+    from soosef.federation.serialization import serialize_record
 
     state = store.state()
     prev_hash = state.head_hash

tests/test_chain_security.py

@@ -15,8 +15,7 @@ import pytest
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
 
 from soosef.exceptions import ChainError
-from soosef.federation.chain import ChainStore, MAX_RECORD_SIZE
-from soosef.federation.serialization import compute_record_hash
+from soosef.federation.chain import MAX_RECORD_SIZE, ChainStore
 
 
 def test_concurrent_append_no_fork(chain_dir: Path):

tests/test_deadman_enforcement.py

@@ -182,10 +182,9 @@ def test_enforcement_loop_tolerates_exceptions(tmp_path: Path, monkeypatch: pyte
 
 def test_start_deadman_thread_is_daemon(monkeypatch: pytest.MonkeyPatch):
     """Thread must be a daemon so it dies with the process."""
-    from soosef.cli import _start_deadman_thread
-
     # Patch the loop to exit immediately so the thread doesn't hang in tests
     import soosef.cli as cli_mod
+    from soosef.cli import _start_deadman_thread
 
     monkeypatch.setattr(cli_mod, "_deadman_enforcement_loop", lambda interval_seconds: None)
 
@@ -208,8 +207,8 @@ def test_check_deadman_disarmed(
     tmp_path: Path, cli_runner: CliRunner, monkeypatch: pytest.MonkeyPatch
 ):
     """check-deadman exits 0 and prints helpful message when not armed."""
-    from soosef.fieldkit import deadman as deadman_mod
     from soosef.cli import main
+    from soosef.fieldkit import deadman as deadman_mod
 
     # Point at an empty tmp dir so the real ~/.soosef/fieldkit/deadman.json isn't read
     state_file = tmp_path / "deadman.json"
@@ -224,8 +223,8 @@ def test_check_deadman_armed_ok(
     tmp_path: Path, cli_runner: CliRunner, monkeypatch: pytest.MonkeyPatch
 ):
     """check-deadman exits 0 when armed and check-in is current."""
-    from soosef.fieldkit import deadman as deadman_mod
     from soosef.cli import main
+    from soosef.fieldkit import deadman as deadman_mod
 
     state_file = tmp_path / "deadman.json"
     monkeypatch.setattr(deadman_mod, "DEADMAN_STATE", state_file)
@@ -248,8 +247,8 @@ def test_check_deadman_overdue_in_grace(
     tmp_path: Path, cli_runner: CliRunner, monkeypatch: pytest.MonkeyPatch
 ):
     """check-deadman exits 0 but prints OVERDUE warning when past interval but in grace."""
-    from soosef.fieldkit import deadman as deadman_mod
     from soosef.cli import main
+    from soosef.fieldkit import deadman as deadman_mod
 
     state_file = tmp_path / "deadman.json"
     monkeypatch.setattr(deadman_mod, "DEADMAN_STATE", state_file)
@@ -274,8 +273,8 @@ def test_check_deadman_fires_when_expired(
     tmp_path: Path, cli_runner: CliRunner, monkeypatch: pytest.MonkeyPatch
 ):
     """check-deadman exits 2 when the switch has fully expired."""
-    from soosef.fieldkit import deadman as deadman_mod
     from soosef.cli import main
+    from soosef.fieldkit import deadman as deadman_mod
 
     state_file = tmp_path / "deadman.json"
     monkeypatch.setattr(deadman_mod, "DEADMAN_STATE", state_file)