feat(merchant): extract merchant portal as first-class frontend with auth, Tailwind fixes, and Gitea CI

- Extract login/dashboard from billing module into core (matching admin pattern)
- Add merchant auth API with path-isolated cookies (path=/merchants)
- Add merchant base layout with sidebar/header partials and Alpine.js init
- Add frontend detection and login redirect for MERCHANT type
- Wire merchant token in shared api-client.js (get/clear)
- Migrate billing templates to merchant base with dark mode support
- Fix Tailwind: rename shop→storefront in sources and config
- DRY Makefile tailwind targets with TAILWIND_FRONTENDS loop
- Rebuild all Tailwind outputs (production minified)
- Add Gitea Actions CI workflow (ruff, pytest, architecture, docs)
- Add Gitea deployment documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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

@@ -3,14 +3,14 @@
 Merchant Billing Page Routes (HTML rendering).
 
 Page routes for the merchant billing portal:
-- Dashboard (overview of stores, subscriptions)
 - Subscriptions list
 - Subscription detail per platform
 - Billing history / invoices
-- Login page
 
 Authentication: merchant_token cookie or Authorization header.
-Login page uses optional auth to check if already logged in.
+
+Login and dashboard routes have moved to core module
+(app/modules/core/routes/pages/merchant.py) to match the admin pattern.
 
 Auto-discovered by the route system (merchant.py in routes/pages/ triggers
 registration under /merchants/billing/*).
@@ -20,10 +20,7 @@ from fastapi import APIRouter, Depends, Path, Request
 from fastapi.responses import HTMLResponse, RedirectResponse
 from sqlalchemy.orm import Session
 
-from app.api.deps import (
-    get_current_merchant_from_cookie_or_header,
-    get_current_merchant_optional,
-)
+from app.api.deps import get_current_merchant_from_cookie_or_header
 from app.core.database import get_db
 from app.modules.core.utils.page_context import get_context_for_frontend
 from app.modules.enums import FrontendType
@@ -53,15 +50,6 @@ def _get_merchant_context(
 
     Uses the module-driven context builder with FrontendType.MERCHANT,
     and adds the authenticated user to the context.
-
-    Args:
-        request: FastAPI request
-        db: Database session
-        current_user: Authenticated merchant user context
-        **extra_context: Additional template variables
-
-    Returns:
-        Dict of context variables for template rendering
     """
     return get_context_for_frontend(
         FrontendType.MERCHANT,
@@ -73,26 +61,14 @@ def _get_merchant_context(
 
 
 # ============================================================================
-# DASHBOARD
+# BILLING ROOT
 # ============================================================================
 
 
-@router.get("/", response_class=HTMLResponse, include_in_schema=False)
-async def merchant_dashboard_page(
-    request: Request,
-    current_user: UserContext = Depends(get_current_merchant_from_cookie_or_header),
-    db: Session = Depends(get_db),
-):
-    """
-    Render merchant dashboard page.
-
-    Shows an overview of the merchant's stores and subscriptions.
-    """
-    context = _get_merchant_context(request, db, current_user)
-    return templates.TemplateResponse(
-        "billing/merchant/dashboard.html",
-        context,
-    )
+@router.get("/", response_class=RedirectResponse, include_in_schema=False)
+async def merchant_billing_root():
+    """Redirect /merchants/billing/ to subscriptions page."""
+    return RedirectResponse(url="/merchants/billing/subscriptions", status_code=302)
 
 
 # ============================================================================
@@ -164,35 +140,3 @@ async def merchant_billing_history_page(
         "billing/merchant/billing-history.html",
         context,
     )
-
-
-# ============================================================================
-# LOGIN
-# ============================================================================
-
-
-@router.get("/login", response_class=HTMLResponse, include_in_schema=False)
-async def merchant_login_page(
-    request: Request,
-    current_user: UserContext | None = Depends(get_current_merchant_optional),
-    db: Session = Depends(get_db),
-):
-    """
-    Render merchant login page.
-
-    If the user is already authenticated as a merchant owner,
-    redirects to the merchant dashboard.
-    """
-    # Redirect to dashboard if already logged in
-    if current_user is not None:
-        return RedirectResponse(url="/merchants/billing/", status_code=302)
-
-    context = get_context_for_frontend(
-        FrontendType.MERCHANT,
-        request,
-        db,
-    )
-    return templates.TemplateResponse(
-        "billing/merchant/login.html",
-        context,
-    )