Add application logging, SMTP email notifications, and supporting changes

Phase 5.4 — Application Logging:
- AppLog model + migration 0010 for unified audit/usage/error logging
- Usage logging middleware in app.py (after_request for /api/* requests)
- Error logging in 500 handler with traceback capture
- Audit logging for auth events (register, login, login_failed, logout,
  password_change) and admin actions (backup, restore, user_delete,
  registration_toggle, smtp_config, smtp_test)
- Admin log viewer (LogsView.vue) with stats, category/search/date
  filters, paginated table with expandable detail rows
- Admin logs API endpoints in admin.py (GET /logs, GET /logs/stats)
- Configurable retention via LOG_RETENTION_DAYS with hourly cleanup

Phase 5.5 — SMTP Email Notifications:
- aiosmtplib dependency for async email sending
- Email service (services/email.py) with STARTTLS/implicit TLS support
- Notification service (services/notifications.py) for security alerts
  and task due date reminders with per-user preferences
- Admin SMTP config endpoints (GET/PUT /api/admin/smtp, POST test)
- SMTP config in Config class with env var + Docker secret support
- Settings UI: notification preferences for all users, SMTP config
  section for admin with test email

Other changes:
- stream_chat() now accepts optional options dict (for num_predict)
- Increase assist MAX_BODY_CHARS from 3000 to 8000
- get_user_by_username() added to auth service
- apiStreamPost buffer processing refactored for robustness
- AppHeader: admin Logs nav link
- Router: /admin/logs route

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

src/fabledassistant/app.py

@@ -1,5 +1,6 @@
 import logging
 import time
+import traceback as tb_module
 from pathlib import Path
 
 from quart import Quart, g, jsonify, make_response, request, send_from_directory
@@ -59,6 +60,24 @@ def create_app() -> Quart:
             response.status_code,
             duration_ms,
         )
+
+        # Log usage for API requests (skip logs endpoint to avoid recursion)
+        if request.path.startswith("/api/") and not request.path.startswith("/api/admin/logs"):
+            try:
+                from fabledassistant.services.logging import log_usage
+
+                user = getattr(g, "user", None)
+                await log_usage(
+                    user_id=user.id if user else None,
+                    username=user.username if user else None,
+                    endpoint=request.path,
+                    method=request.method,
+                    status_code=response.status_code,
+                    duration_ms=duration_ms,
+                )
+            except Exception:
+                logger.debug("Failed to log usage", exc_info=True)
+
         return response
 
     @app.before_serving
@@ -67,8 +86,12 @@ def create_app() -> Quart:
 
         from fabledassistant.services.generation_buffer import start_cleanup_loop
         from fabledassistant.services.llm import ensure_model
+        from fabledassistant.services.logging import start_log_retention_loop
+        from fabledassistant.services.notifications import start_notification_loop
 
         start_cleanup_loop()
+        start_log_retention_loop()
+        start_notification_loop()
 
         async def _pull_model():
             try:
@@ -111,6 +134,23 @@ def create_app() -> Quart:
     @app.errorhandler(500)
     async def handle_500(error):
         logger.exception("Internal server error on %s %s", request.method, request.path)
+
+        try:
+            from fabledassistant.services.logging import log_error
+
+            user = getattr(g, "user", None)
+            await log_error(
+                user_id=user.id if user else None,
+                username=user.username if user else None,
+                endpoint=request.path,
+                method=request.method,
+                error_type=type(error).__name__,
+                error_message=str(error),
+                traceback=tb_module.format_exc(),
+            )
+        except Exception:
+            logger.debug("Failed to log error", exc_info=True)
+
         if request.path.startswith("/api/"):
             return jsonify({"error": "Internal server error"}), 500
         return "Internal Server Error", 500