feat(subscriptions): add SaaS subscription tiers, pricing page, and enforced upload quotas

- Add Free / Starter / Professional / Business tiers with lifetime, daily, and monthly
  file limits (app/utils/subscription.py)
- Add subscription_tier column to UserProfile model + migration 014
- Enforce quotas at upload time (HTTP 402 on violation) in /api/ui-upload
- New REST API: GET /api/subscriptions/tiers, /my, /platform (admin)
- New pages: /pricing (marketing, public) and /subscription (per-user status)
- Enhanced dashboard: SaaS stats (files today/month, OCR count, active users)
  in multi-user mode; original single-user layout preserved
- Admin users page: show Plan badge, allow tier editing via dropdown
- Navigation: add Pricing link + subscription icon in user header
- Tests: 23 unit tests for subscription tier logic
- Docs: docs/SubscriptionTiers.md

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/views/subscriptions.py

@@ -0,0 +1,64 @@
+"""View routes for subscription-related pages.
+
+Routes:
+  GET /pricing          — public marketing pricing page
+  GET /subscription     — authenticated user's current plan & usage
+"""
+
+import logging
+
+from fastapi import Depends, Request
+from sqlalchemy.orm import Session
+
+from app.utils.subscription import TIER_ORDER, get_all_tiers, get_tier, get_user_tier_id, get_user_usage
+from app.views.base import APIRouter, get_db, require_login, templates
+
+logger = logging.getLogger(__name__)
+router = APIRouter()
+
+
+@router.get("/pricing", include_in_schema=False)
+async def pricing_page(request: Request):
+    """Public-facing pricing and plans page."""
+    tiers = get_all_tiers()
+    return templates.TemplateResponse(
+        "pricing.html",
+        {
+            "request": request,
+            "tiers": tiers,
+            "tier_order": TIER_ORDER,
+        },
+    )
+
+
+@router.get("/subscription", include_in_schema=False)
+@require_login
+async def my_subscription_page(request: Request, db: Session = Depends(get_db)):
+    """Authenticated user's subscription status and usage page."""
+    from app.config import settings
+
+    user = request.session.get("user") or {}
+    owner_id: str = user.get("username") or user.get("email") or user.get("sub") or ""
+
+    if settings.multi_user_enabled and owner_id:
+        tier_id = get_user_tier_id(db, owner_id)
+        usage = get_user_usage(db, owner_id)
+    else:
+        tier_id = "business"
+        usage = None
+
+    tier = get_tier(tier_id)
+    all_tiers = get_all_tiers()
+
+    return templates.TemplateResponse(
+        "subscription.html",
+        {
+            "request": request,
+            "tier": tier,
+            "tier_id": tier_id,
+            "usage": usage,
+            "all_tiers": all_tiers,
+            "multi_user_enabled": settings.multi_user_enabled,
+            "owner_id": owner_id,
+        },
+    )