fix(audit): P0-P3 audit fixes — 838 ruff errors → 0, 30 F821 bugs fixed, 118 files changed

- P0: hooks.py 3-tuple fix, trigger_dispatcher Contract, contacts/plugin unregister_actions_by_owner
- P0: 5 test files — check_permission mocks removed, hardcoded DB credential → env var
- P1: attachment_service DmsFile via Contract helper, restore_registry/history_hooks dedup
- P1: mail/plugin restore unregister, mcp_client datetime.now(UTC), saved_views/filters patterns
- P1: ProtectedRoute fail-closed, 13 test assertion fixes (bcrypt, DB-URLs, SECRET_KEYs)
- P2: deprecated notifications → post_system_message (3 files), forgejo Base, report_generator lazy import
- P2: webhooks permissions, deps.py/roles.py plugin perms removed, import_export default
- P2: address/tags/entity_links patterns removed, worker.py Contract-Umgehungen fixed
- P2: 28 frontend TODOs (hardcoded constants, deprecated notification API)
- P3: dead code, duplicates, deprecated imports, private attr, __import__ inline
- P3: 8 frontend TODOs (LucideIcons, inline styles, XSS, i18n)
- ruff: 838 → 0 (612 auto-fix + 246 manual + 27 F821 regression fix)
- F821: 30 → 0 (AutomationDefinition, DmsFile, user_id, Path, Any, String)
- Contract-Umgehungen: 2 neue gefunden (worker.py:169, worker.py:280) und gefixt

app/services/dedup_service.py

@@ -1,17 +1,25 @@
-"""Deduplication / merge service for contacts."""
+"""Contact deduplication / merge service.
+
+This service is Contact-specific — it handles duplicate detection and merging
+for the Contact entity only. It is NOT a generic dedup service. If other
+entity types need dedup in the future, a separate service or a plugin-based
+interface should be created.
+
+Declared as Contact-specific (P1-22 fix): no pretense of being generic.
+"""
 
 from __future__ import annotations
 
 import uuid
+from datetime import UTC
 from typing import Any
 
-from sqlalchemy import select, func, text
+from sqlalchemy import func, select, text
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.models.contact import Contact
 from app.models.contact_merge import ContactMergeHistory
 
-
 # Fields used for duplicate detection
 DUPLICATE_FIELDS = [
     "displayname", "name", "firstname", "surname",
@@ -168,7 +176,7 @@ async def find_duplicates(
             name_map.setdefault(norm, []).append(c)
 
     # Find contacts with same normalized name
-    for norm_name, group in name_map.items():
+    for _norm_name, group in name_map.items():
         if len(group) < 2:
             continue
         for i in range(len(group)):
@@ -314,8 +322,8 @@ async def merge_contacts(
     )
 
     # Soft-delete the source contact
-    from datetime import datetime, timezone
-    source.deleted_at = datetime.now(timezone.utc)
+    from datetime import datetime
+    source.deleted_at = datetime.now(UTC)
 
     # Record merge history
     history = ContactMergeHistory(