feat(test-catalog): add template creation and lead-approval workflow

Leads get a Create Template button that adds directly to the catalog
(existing POST /test-templates). Operators (red_tech/blue_tech) get the
same button, but their proposal now lands in a new template_suggestions
review queue instead — a lead on their team can approve it as-is, edit
fields before approving, or discard it. Modeled on the existing
ProcedureSuggestion review workflow.

backend/app/schemas/template_suggestion.py

@@ -0,0 +1,72 @@
+"""Pydantic schemas for the TemplateSuggestion (operator template proposal) workflow."""
+
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+
+class TemplateSuggestionCreate(BaseModel):
+    """Payload for an operator proposing a new test template."""
+
+    mitre_technique_id: str
+    name: str
+    description: str | None = None
+    source: str = "custom"
+    source_url: str | None = None
+    attack_procedure: str | None = None
+    expected_detection: str | None = None
+    platform: str | None = None
+    tool_suggested: str | None = None
+    severity: str | None = None
+    atomic_test_id: str | None = None
+    suggested_remediation: str | None = None
+
+
+class TemplateSuggestionApprove(BaseModel):
+    """Optional field overrides a lead can apply while approving a suggestion.
+
+    Any field left unset falls back to what the operator originally
+    submitted — the lead only needs to pass the fields they want to change.
+    """
+
+    mitre_technique_id: str | None = None
+    name: str | None = None
+    description: str | None = None
+    source: str | None = None
+    source_url: str | None = None
+    attack_procedure: str | None = None
+    expected_detection: str | None = None
+    platform: str | None = None
+    tool_suggested: str | None = None
+    severity: str | None = None
+    atomic_test_id: str | None = None
+    suggested_remediation: str | None = None
+
+
+class TemplateSuggestionOut(BaseModel):
+    """Full representation of a pending/reviewed template suggestion."""
+
+    id: uuid.UUID
+    mitre_technique_id: str
+    name: str
+    description: str | None = None
+    source: str
+    source_url: str | None = None
+    attack_procedure: str | None = None
+    expected_detection: str | None = None
+    platform: str | None = None
+    tool_suggested: str | None = None
+    severity: str | None = None
+    atomic_test_id: str | None = None
+    suggested_remediation: str | None = None
+    team: str
+    submitted_by: uuid.UUID | None = None
+    submitter_name: str | None = None
+    status: str
+    reviewed_by: uuid.UUID | None = None
+    reviewed_at: datetime | None = None
+    created_template_id: uuid.UUID | None = None
+    created_at: datetime | None = None
+
+    model_config = ConfigDict(from_attributes=True)