fix(build): 重命名 requirement.txt 并统一所有引用

- 重命名 requirement.txt → requirements.txt
- 更新 build.yml 和 build-test.yml 中的 pip cache 和
  install 路径引用
- README.md 恢复 pip install -r requirements.txt 构建步骤

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/build-test.yml

@@ -45,12 +45,12 @@ jobs:
       with:
         python-version: '3.13'
         cache: 'pip'
-        cache-dependency-path: requirement.txt
+        cache-dependency-path: requirements.txt
 
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -r requirement.txt
+        pip install -r requirements.txt
 
     - name: Solve ddddocr compatibility and copy model files
       run: |

.github/workflows/build.yml

@@ -86,12 +86,12 @@ jobs:
       with:
         python-version: '3.13'
         cache: 'pip'
-        cache-dependency-path: requirement.txt
+        cache-dependency-path: requirements.txt
 
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -r requirement.txt
+        pip install -r requirements.txt
 
     - name: Solve ddddocr compatibility and copy model files
       run: |