refactor: rename public routes and templates to platform

Complete the public -> platform naming migration across the codebase.
This aligns with the naming convention where "platform" refers to
the marketing/public-facing pages of the platform itself.

Changes:
- Update all imports from public to platform modules
- Update template references from public/ to platform/
- Update route registrations to use platform prefix
- Update documentation to reflect new naming
- Update test files for platform API endpoints

Files affected:
- app/api/main.py - router imports
- app/modules/*/routes/*/platform.py - route definitions
- app/modules/*/templates/*/platform/ - template files
- app/modules/routes.py - route discovery
- docs/* - documentation updates
- tests/integration/api/v1/platform/ - test files

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/billing/routes/pages/platform.py

@@ -1,8 +1,8 @@
-# app/modules/billing/routes/pages/public.py
+# app/modules/billing/routes/pages/platform.py
 """
-Billing Public Page Routes (HTML rendering).
+Billing Platform Page Routes (HTML rendering).
 
-Public (unauthenticated) pages for pricing and signup:
+Platform (unauthenticated) pages for pricing and signup:
 - Pricing page
 - Signup wizard
 - Signup success
@@ -14,7 +14,7 @@ from sqlalchemy.orm import Session
 
 from app.core.database import get_db
 from app.modules.billing.models import TIER_LIMITS, TierCode
-from app.modules.core.utils.page_context import get_public_context
+from app.modules.core.utils.page_context import get_platform_context
 from app.templates_config import templates
 
 router = APIRouter()
@@ -57,12 +57,12 @@ async def pricing_page(
     """
     Standalone pricing page with detailed tier comparison.
     """
-    context = get_public_context(request, db)
+    context = get_platform_context(request, db)
     context["tiers"] = _get_tiers_data()
     context["page_title"] = "Pricing"
 
     return templates.TemplateResponse(
-        "billing/public/pricing.html",
+        "billing/platform/pricing.html",
         context,
     )
 
@@ -86,14 +86,14 @@ async def signup_page(
     - tier: Pre-selected tier code
     - annual: Pre-select annual billing
     """
-    context = get_public_context(request, db)
+    context = get_platform_context(request, db)
     context["page_title"] = "Start Your Free Trial"
     context["selected_tier"] = tier
     context["is_annual"] = annual
     context["tiers"] = _get_tiers_data()
 
     return templates.TemplateResponse(
-        "billing/public/signup.html",
+        "billing/platform/signup.html",
         context,
     )
 
@@ -111,11 +111,11 @@ async def signup_success_page(
 
     Shown after successful account creation.
     """
-    context = get_public_context(request, db)
+    context = get_platform_context(request, db)
     context["page_title"] = "Welcome to Wizamart!"
     context["vendor_code"] = vendor_code
 
     return templates.TemplateResponse(
-        "billing/public/signup-success.html",
+        "billing/platform/signup-success.html",
         context,
     )