refactor(catalog)!: decouple materials from categories (v2.7)

Materials are now global and category-free. The category lives only on the supplier (suppliers.category_id); every category-facing query goes through the supplier edge instead of the material row.

Schema (migration.sql + init_db DDL):
- drop the materials.category_id column, its FK, and the v2.5 first-link-wins automation (fn_derive_material_category + trg_supplier_materials_derive_category) — the DDL runs idempotently at API startup

Backend:
- GET /materials?category_id=… now filters via EXISTS(supplier_materials ⋈ suppliers.category_id)
- quote category filters (quotes list) use the quote's supplier category
- /pm/on-the-way derives the display category from the supplier of the quote
- supplier_materials links no longer derive/return a material category
- expand_service: material expand=category resolves to null (kept for contract compatibility)
- material create/update no longer validates or stores category_id; seed.py aligned

Frontend:
- material creation no longer sends category_id
- formatMaterialTitle reworked to a strict order with « . » separator: [Brand] . [Material] . [Spec 1] . [Spec 2], brand deduped when the stored name already starts with it; specs separator switched from « · » to « . »

Validated: python compile, api + frontend image builds (tsc + vite) clean; branch cut from the tip of prod_v4 (= origin/production, 5a9ef40 — the team's merge made them identical).

backend/app/services/expand_service.py

@@ -206,11 +206,6 @@ async def _load_material_maps(db: AsyncSession, materials: list[Material], expan
     material_ids = [m.id for m in materials]
     maps: dict = {"categories": {}, "units": {}, "brands": {}, "material_brands": {}, "mavs": {}, "attr_defs": {}}
 
-    if "category" in expand:
-        cat_ids = {m.category_id for m in materials}
-        rows = (await db.execute(select(MaterialCategory).where(MaterialCategory.id.in_(cat_ids)))).scalars().all()
-        maps["categories"] = {c.id: c for c in rows}
-
     unit_ids: set[int] = set()
     if "canonical_unit" in expand:
         unit_ids |= {m.canonical_unit_id for m in materials}
@@ -258,9 +253,9 @@ def _material_to_dict(m: Material, expand: set[str], maps: dict) -> dict:
         "updated_at": to_iso(m.updated_at),
     }
     if "category" in expand:
-        d["category"] = category_brief(maps["categories"].get(m.category_id))
+        d["category"] = None
     else:
-        d["category_id"] = str(m.category_id)
+        d["category_id"] = None
     if "canonical_unit" in expand:
         d["canonical_unit"] = unit_to_dict(maps["units"].get(m.canonical_unit_id))
     else:
@@ -326,9 +321,6 @@ async def _load_line_item_data(db: AsyncSession, line_items: list[LineItem], exp
         material_ids = {li.material_id for li in line_items}
         materials = (await db.execute(select(Material).where(Material.id.in_(material_ids)))).scalars().all()
         data.materials = {m.id: m for m in materials}
-        cat_ids = {m.category_id for m in materials}
-        cats = (await db.execute(select(MaterialCategory).where(MaterialCategory.id.in_(cat_ids)))).scalars().all()
-        data.categories = {c.id: c for c in cats}
         bms = (await db.execute(select(BrandMaterial).where(BrandMaterial.material_id.in_(material_ids)))).scalars().all()
         brand_ids: set[uuid.UUID] = set()
         for bm in bms:
@@ -450,7 +442,7 @@ def _line_item_expanded(li: LineItem, expand: set[str], data: _LineItemData, inc
             d["material"] = {
                 "id": str(m.id),
                 "name": m.name,
-                "category": category_brief(data.categories.get(m.category_id)),
+                "category": None,
                 "brands": [
                     {"id": str(bm.brand_id), "name": data.brands[bm.brand_id].name, "catalog_code": bm.catalog_code}
                     for bm in data.material_brands.get(m.id, [])

backend/app/services/material_service.py

@@ -12,7 +12,6 @@ from app.models.catalog import (
     BrandMaterial,
     Material,
     MaterialAttributeValue,
-    MaterialCategory,
     Unit,
 )
 from app.schemas.catalog import MaterialAttributeIn, MaterialCreate, MaterialUpdate
@@ -110,9 +109,7 @@ async def validate_attributes(
 async def create_material(db: AsyncSession, payload: MaterialCreate) -> Material:
     """Create a material + brand_materials rows + EAV values in ONE transaction.
 
-    v2.5/2.6: category_id is OPTIONAL — a global material may be created
-    without a category (it gets derived automatically from the first linked
-    supplier). name is GLOBALLY unique.
+    v2.6/v2.7: materials are global and category-free. name is GLOBALLY unique.
     """
     async with db.begin():
         duplicate = await db.scalar(
@@ -121,14 +118,10 @@ async def create_material(db: AsyncSession, payload: MaterialCreate) -> Material
         if duplicate is not None:
             raise ConflictError("متریالی با این نام در کل کاتالوگ قبلاً ثبت شده است", field="name")
 
-        if payload.category_id is not None:
-            if await db.get(MaterialCategory, payload.category_id) is None:
-                raise NotFoundError("دسته‌بندی یافت نشد", field="category_id")
         if not await db.get(Unit, payload.canonical_unit_id):
             raise NotFoundError("واحد مرجع یافت نشد", field="canonical_unit_id")
 
         material = Material(
-            category_id=payload.category_id,
             name=payload.name,
             topic=payload.topic,
             canonical_unit_id=payload.canonical_unit_id,

backend/app/services/quote_service.py

@@ -903,15 +903,12 @@ async def quote_stats(
 
 
 def _quote_has_category(category_id: UUID):
-    """EXISTS: quote has a line item whose material belongs to category_id."""
-    from app.models.catalog import Material
-
+    """EXISTS: quote's supplier belongs to category_id."""
     sub = (
         select(1)
         .where(
-            LineItem.quote_id == Quote.id,
-            Material.id == LineItem.material_id,
-            Material.category_id == category_id,
+            Supplier.id == Quote.supplier_id,
+            Supplier.category_id == category_id,
         )
     )
     return func.exists(sub)

backend/app/services/supplier_material_service.py

@@ -1,10 +1,6 @@
-"""Supplier ↔ material link service (v2.5) — the direct edge of the new flow.
+"""Supplier ↔ material link service (v2.6/v2.7) — the direct edge of the catalog flow.
 
-Linking a material to a supplier derives materials.category_id from the
-supplier's category when the material has none (first-link-wins). The same
-rule is enforced by the DB trigger trg_supplier_materials_derive_category;
-this service applies it in the application layer so the ORM state is
-consistent inside the same transaction.
+Suppliers can supply any global material across categories.
 """
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -17,7 +13,7 @@ from app.utils.errors import NotFoundError, ValidationError
 async def link_supplier_material(
     db: AsyncSession, supplier_id, material_id, is_active: bool = True
 ) -> SupplierMaterial:
-    """Upsert a supplier<->material link (idempotent) + derive category (first-link-wins).
+    """Upsert a supplier<->material link (idempotent).
 
     Caller is responsible for the surrounding transaction.
     """
@@ -42,15 +38,11 @@ async def link_supplier_material(
     link = SupplierMaterial(supplier_id=supplier_id, material_id=material_id, is_active=is_active)
     db.add(link)
     await db.flush()
-
-    # First-link-wins: only when the material has no category yet.
-    if material.category_id is None:
-        material.category_id = supplier.category_id
     return link
 
 
 async def unlink_supplier_material(db: AsyncSession, supplier_id, material_id) -> None:
-    """Remove the link. The material's category is NEVER auto-cleared (documented rule)."""
+    """Remove the link."""
     link = await db.scalar(
         select(SupplierMaterial).where(
             SupplierMaterial.supplier_id == supplier_id,