Phase 25: templates as stack folders (0.31.0)

Templates are now stack-shaped folders (compose.yaml + .env.example +
template.json) instead of DB rows + manifest.json + {{VAR}} rendering.
Pull copies the folder into a new stack; custom templates persist under
DATA_DIR/templates. Adds POST /api/templates/from-stack and a one-time
startup migration for pre-0.31 DB templates (drops the template table).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/models/__init__.py

@@ -6,10 +6,9 @@ from models.backup_destination import BackupDestination
 from models.backup_schedule import BackupSchedule
 from models.setting import Setting, Webhook
 from models.stack import Stack
-from models.template import Template
 from models.user import User
 
 __all__ = [
-    "User", "Stack", "AuditLog", "Template", "Setting", "Webhook", "Agent",
+    "User", "Stack", "AuditLog", "Setting", "Webhook", "Agent",
     "BackupDestination", "BackupSchedule", "AutoUpdate",
 ]

backend/models/template.py

@@ -1,34 +1,11 @@
 from __future__ import annotations
 
-from datetime import datetime, timezone
 from typing import Optional
 
-from sqlmodel import Field, SQLModel
+from sqlmodel import SQLModel
 
-
-def _now() -> datetime:
-    return datetime.now(timezone.utc)
-
-
-class Template(SQLModel, table=True):
-    """User-saved custom template (bundled ones live on disk)."""
-
-    id: Optional[int] = Field(default=None, primary_key=True)
-    slug: str = Field(index=True, unique=True)
-    name: str
-    description: Optional[str] = None
-    tags: str = ""  # comma separated
-    yaml: str = ""
-    created_at: datetime = Field(default_factory=_now)
-
-
-# --- API schemas ---
-
-
-class TemplateVariable(SQLModel):
-    name: str
-    description: str = ""
-    default: str = ""
+# Templates are stored as stack-shaped folders on disk (see
+# services/template_service.py), not in the database. These are API schemas only.
 
 
 class TemplateSummary(SQLModel):
@@ -41,18 +18,26 @@ class TemplateSummary(SQLModel):
 
 
 class TemplateDetail(TemplateSummary):
-    yaml: str
-    variables: list[TemplateVariable] = []
+    compose: str = ""
+    env: str = ""
+    files: list[str] = []  # relative paths the template ships
 
 
 class TemplateSaveRequest(SQLModel):
     name: str
     description: Optional[str] = None
     tags: list[str] = []
-    yaml: str
+    gpu: Optional[str] = None
+    compose: str
+    env: str = ""
+
+
+class TemplateFromStackRequest(SQLModel):
+    stack_id: str
+    name: str
+    description: Optional[str] = None
 
 
 class TemplateInstantiateRequest(SQLModel):
     name: str  # new stack name
-    values: dict[str, str] = {}
     agent_id: int | None = None  # None = local host; otherwise deploy to a remote agent