fix(ci): isolate GOMODCACHE per job to prevent cache conflicts

Move GOMODCACHE from global env to job-level env with unique paths per job. Prevents race conditions and cache corruption when jobs run in parallel, especially after the gotextdiff mirror replacement.

.gitea/workflows/build.yml

@@ -16,7 +16,6 @@ env:
   GOPRIVATE: git.marketally.com
   GONOSUMDB: git.marketally.com
   GOTOOLCHAIN: local
-  GOMODCACHE: /tmp/gomod-${{ github.run_id }}-${{ github.job }}
   GO_VERSION: "1.25.5"
   NODE_VERSION: "22"
 
@@ -25,6 +24,8 @@ jobs:
   lint:
     name: Lint
     runs-on: linux-latest
+    env:
+      GOMODCACHE: /tmp/gomod-${{ github.run_id }}-lint
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -66,6 +67,8 @@ jobs:
   test-unit:
     name: Unit Tests
     runs-on: linux-latest
+    env:
+      GOMODCACHE: /tmp/gomod-${{ github.run_id }}-unit
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
@@ -102,6 +105,8 @@ jobs:
   test-pgsql:
     name: Integration Tests (PostgreSQL)
     runs-on: linux-latest
+    env:
+      GOMODCACHE: /tmp/gomod-${{ github.run_id }}-pgsql
     services:
       pgsql:
         image: postgres:15