feat: fix template preview links, default chat action, update default templates

- Fix sanitizePreview regex to match literal quotes instead of " entities
- Default telegram chat_action to "typing" in model and frontend
- Change "photo(s)" to "file(s)" in default templates (EN/RU)
- Remove redundant album URL line from assets_added templates
- Auto-refresh system-owned templates from files on server startup

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

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

@@ -164,7 +164,7 @@ class NotificationTarget(SQLModel, table=True):
     name: str
     icon: str = Field(default="")
     config: dict[str, Any] = Field(default_factory=dict, sa_column=Column(JSON))
-    chat_action: str | None = Field(default=None)  # e.g. "typing", "upload_photo"
+    chat_action: str | None = Field(default="typing")  # e.g. "typing", "upload_photo"
     created_at: datetime = Field(default_factory=_utcnow)