templates: add netmiko_device_type for automation tools

Common template field (schema + templates table column + Alembic
migration) holding the Netmiko device type (e.g. 'cisco_xr', 'nokia_srl')
so Netmiko/Nornir based tooling can look up how to reach a node's CLI
without hard-coded vendor mappings. Free-form lowercase string on
purpose: Netmiko's platform list evolves independently of GNS3.

gns3server/db/models/templates.py

@@ -35,6 +35,7 @@ class Template(BaseTable):
     symbol = Column(String)
     builtin = Column(Boolean, default=False)
     usage = Column(String)
+    netmiko_device_type = Column(String)
     template_type = Column(String)
     tags = Column(JSON)
     compute_id = Column(String)

gns3server/db_migrations/versions/b3c7e2a91d4f_add_netmiko_device_type_to_templates.py

@@ -0,0 +1,26 @@
+"""add netmiko_device_type to templates table
+
+Revision ID: b3c7e2a91d4f
+Revises: 8f2a1c4e9d3b
+Create Date: 2026-08-16 10:00:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'b3c7e2a91d4f'
+down_revision = '8f2a1c4e9d3b'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+
+    op.add_column('templates', sa.Column('netmiko_device_type', sa.String()))
+
+
+def downgrade() -> None:
+
+    op.drop_column('templates', 'netmiko_device_type')

gns3server/schemas/controller/templates/__init__.py

@@ -48,6 +48,11 @@ class TemplateBase(BaseModel):
     template_type: Optional[NodeType] = None
     compute_id: Optional[str] = None
     usage: Optional[str] = ""
+    netmiko_device_type: Optional[str] = Field(
+        None,
+        description="Device type for Netmiko-based automation tools (e.g. 'cisco_xr' or 'nokia_srl')",
+        pattern=r"^[a-z0-9_]+$",
+    )
     tags: Optional[List[str]] = Field(
         default_factory=list,
         description="User-defined metadata tags (e.g. 'vendor:cisco' or 'model:7200')"