feat: Discord/Slack/ntfy/Matrix targets, command templates, delete protection, email/matrix bots

- Discord, Slack, ntfy, Matrix notification target types with clients and dispatch
- MatrixBot model + API + frontend in Bots tab
- Command template system fully wired into all handler commands
- Default command templates seeded (EN/RU, 14 slots each)
- Command template editor with variables reference including child fields
- Delete protection on all 10 entity types (409 with consumer details)
- Provider type selector on template config forms
- Target type selector as dropdown with all 7 types
- Response template selector on command config form
- CLAUDE.md: mandatory server restart rule, child properties rule

packages/server/src/notify_bridge_server/database/models.py

@@ -53,6 +53,21 @@ class TelegramBot(SQLModel, table=True):
     created_at: datetime = Field(default_factory=_utcnow)
 
 
+class MatrixBot(SQLModel, table=True):
+    """Matrix bot — homeserver connection for sending messages to rooms."""
+
+    __tablename__ = "matrix_bot"
+
+    id: int | None = Field(default=None, primary_key=True)
+    user_id: int = Field(foreign_key="user.id")
+    name: str
+    icon: str = Field(default="")
+    homeserver_url: str  # e.g. https://matrix.org
+    access_token: str
+    display_name: str = Field(default="")
+    created_at: datetime = Field(default_factory=_utcnow)
+
+
 class EmailBot(SQLModel, table=True):
     """Email sender — SMTP connection for sending email notifications."""
 
@@ -190,7 +205,7 @@ class NotificationTarget(SQLModel, table=True):
 
     id: int | None = Field(default=None, primary_key=True)
     user_id: int = Field(foreign_key="user.id")
-    type: str  # "telegram", "webhook", or "email"
+    type: str  # "telegram", "webhook", "email", "discord", "slack", "ntfy", "matrix"
     name: str
     icon: str = Field(default="")
     config: dict[str, Any] = Field(default_factory=dict, sa_column=Column(JSON))