ci: add explicit contents:read permissions to workflows

Addresses 'Workflow does not contain permissions' security warning by
declaring least-privilege GITHUB_TOKEN scopes for all CI workflows.

Fixes #52

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Tranquility2

.github/workflows/bandit.yml

@@ -1,6 +1,9 @@
 name: Bandit
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Bandit Validation

.github/workflows/black.yml

@@ -1,6 +1,9 @@
 name: Black
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Black Validation

.github/workflows/coverage.yml

@@ -1,6 +1,9 @@
 name: Coverage
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Coverage Validation

.github/workflows/isort.yml

@@ -1,6 +1,9 @@
 name: Isort
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Isort Validation

.github/workflows/mypy.yml

@@ -1,6 +1,9 @@
 name: Mypy
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Mypy Validation

.github/workflows/pylint.yml

@@ -1,6 +1,9 @@
 name: Pylint
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Pylint Validation

.github/workflows/pytest.yml

@@ -1,6 +1,9 @@
 name: Pytest
 on: [ pull_request, workflow_dispatch ]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Pytest Validation