chore(ci): comprehensive CI/CD audit fixes per best practices

Implements all 13 fixes identified in the CI/CD audit against
github-actions-ci-cd-best-practices.instructions.md

Critical fixes:

Remove hardcoded encryption key from playwright.yml (security)
Fix artifact filename mismatch in supply-chain-pr.yml (bug)
Pin GoReleaser to ~> v2.5 instead of latest (supply chain)
High priority fixes:

Upgrade CodeQL action from v3 to v4 in supply-chain-pr.yml
Add environment protection for release workflow
Fix shell variable escaping ($$ → $) in release-goreleaser.yml
Medium priority fixes:

Add timeout-minutes to playwright.yml (20 min)
Add explicit permissions to quality-checks.yml
Add timeout-minutes to codecov-upload.yml jobs (15 min)
Fix benchmark.yml permissions (workflow-level read, job-level write)
Low priority fixes:

Add timeout-minutes to docs.yml jobs (10/5 min)
Add permissions block to docker-lint.yml
Add timeout-minutes to renovate.yml (30 min)

.github/workflows/codecov-upload.yml

@@ -22,6 +22,7 @@ jobs:
   backend-codecov:
     name: Backend Codecov Upload
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     steps:
       - name: Checkout
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
@@ -53,6 +54,7 @@ jobs:
   frontend-codecov:
     name: Frontend Codecov Upload
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     steps:
       - name: Checkout
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6