ci: add timeout-minutes to all workflow jobs

Prevents hung runners on pathological failures. Every job now has
timeout-minutes: 15.

Co-Authored-By: claude-flow <ruv@ruv.net>

Author: fidgetcoding

.github/workflows/lint.yml

@@ -20,6 +20,7 @@ permissions:
 jobs:
   shellcheck:
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     steps:
       - uses: actions/checkout@v6
       - name: Run ShellCheck

.github/workflows/security.yml

@@ -19,6 +19,7 @@ jobs:
   shellcheck-strict:
     name: ShellCheck (error severity)
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     steps:
       - uses: actions/checkout@v6
       - name: Run ShellCheck at error severity
@@ -31,6 +32,7 @@ jobs:
   secret-scan:
     name: Secret scanning
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     steps:
       - uses: actions/checkout@v6
         with: