ci: restrict GITHUB_TOKEN permissions to least privilege

Add explicit permissions blocks to all workflows to limit the scope
of the GITHUB_TOKEN rather than relying on the broad default permissions.

- build.yml: contents: read (checkout + artifacts)
- check-offline-permissions.yml: contents: read
- unsigned-release.yml: contents: read
- create-release.yml: contents: write (create release + upload assets)
- crowdin.yml: contents: write + pull-requests: write (push translations, open PRs)

https://claude.ai/code/session_012jEe5WfLkonuFPNZ7q7fKc

.github/workflows/build.yml

@@ -6,6 +6,9 @@ on:
   push:
     branches: [master]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     runs-on: ubuntu-latest

.github/workflows/check-offline-permissions.yml

@@ -6,6 +6,9 @@ on:
   push:
     branches: [master]
 
+permissions:
+  contents: read
+
 jobs:
   check-offline-permissions:
     runs-on: ubuntu-latest

.github/workflows/create-release.yml

@@ -5,6 +5,9 @@ on:
     tags:
     - 'v*' # Push events to matching v*, i.e. v1.0, v20.15.10
 
+permissions:
+  contents: write
+
 jobs:
   deploy:
     runs-on: ubuntu-latest

.github/workflows/crowdin.yml

@@ -4,6 +4,10 @@ on:
   push:
     branches: [ master ]
 
+permissions:
+  contents: write
+  pull-requests: write
+
 jobs:
   synchronize-with-crowdin:
     runs-on: ubuntu-latest

.github/workflows/unsigned-release.yml

@@ -5,6 +5,9 @@ on:
     tags:
       - 'v*'
 
+permissions:
+  contents: read
+
 jobs:
   build:
     runs-on: ubuntu-latest