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/models/__init__.py

@@ -15,3 +15,4 @@ from fabledassistant.models.note import Note, TaskPriority, TaskStatus  # noqa:
 from fabledassistant.models.conversation import Conversation, Message  # noqa: E402, F401
 from fabledassistant.models.setting import Setting  # noqa: E402, F401
 from fabledassistant.models.user import User  # noqa: E402, F401
+from fabledassistant.models.app_log import AppLog  # noqa: E402, F401

src/fabledassistant/models/app_log.py

@@ -0,0 +1,48 @@
+from datetime import datetime, timezone
+
+from sqlalchemy import DateTime, Float, Index, Integer, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from fabledassistant.models import Base
+
+
+class AppLog(Base):
+    __tablename__ = "app_logs"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    category: Mapped[str] = mapped_column(Text, nullable=False)
+    user_id: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    username: Mapped[str | None] = mapped_column(Text, nullable=True)
+    action: Mapped[str | None] = mapped_column(Text, nullable=True)
+    endpoint: Mapped[str | None] = mapped_column(Text, nullable=True)
+    method: Mapped[str | None] = mapped_column(Text, nullable=True)
+    status_code: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    duration_ms: Mapped[float | None] = mapped_column(Float, nullable=True)
+    ip_address: Mapped[str | None] = mapped_column(Text, nullable=True)
+    details: Mapped[str | None] = mapped_column(Text, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+
+    __table_args__ = (
+        Index("ix_app_logs_category", "category"),
+        Index("ix_app_logs_user_id", "user_id"),
+        Index("ix_app_logs_created_at", "created_at"),
+        Index("ix_app_logs_category_created_at", "category", created_at.desc()),
+    )
+
+    def to_dict(self) -> dict:
+        return {
+            "id": self.id,
+            "category": self.category,
+            "user_id": self.user_id,
+            "username": self.username,
+            "action": self.action,
+            "endpoint": self.endpoint,
+            "method": self.method,
+            "status_code": self.status_code,
+            "duration_ms": self.duration_ms,
+            "ip_address": self.ip_address,
+            "details": self.details,
+            "created_at": self.created_at.isoformat() if self.created_at else None,
+        }