feat(hosting): add industry template infrastructure (Workstream 3B)

5 industry templates as JSON presets, each with theme + multi-page content:
- generic: clean minimal (homepage, about, contact)
- restaurant: warm tones, Playfair Display (homepage, about, menu, contact)
- construction: amber/earth tones, Montserrat (homepage, services, projects, contact)
- auto-parts: red/bold, parts-focused (homepage, catalog, contact)
- professional-services: navy/blue, Merriweather (homepage, services, team, contact)

Each template has:
- meta.json (name, description, tags, languages)
- theme.json (colors, fonts, layout, header style)
- pages/*.json (section-based homepage + content pages with i18n)
- {{placeholder}} variables for prospect data injection

TemplateService loads from templates_library/ directory with caching.
GET /admin/hosting/sites/templates endpoint to list available templates.

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

app/modules/hosting/schemas/template.py

@@ -0,0 +1,21 @@
+# app/modules/hosting/schemas/template.py
+"""Pydantic schemas for template responses."""
+
+from pydantic import BaseModel
+
+
+class TemplateResponse(BaseModel):
+    """Schema for a single template."""
+
+    id: str
+    name: str
+    description: str
+    tags: list[str] = []
+    languages: list[str] = []
+    pages: list[str] = []
+
+
+class TemplateListResponse(BaseModel):
+    """Schema for template list response."""
+
+    templates: list[TemplateResponse]