ci: reuse shared Python dependency cache across workflows (#7693)

# Description of Changes

This PR removes workflow-specific cache suffixes from Python dependency
caching in several CI workflows.

Previously, the following workflows appended their own `cache-suffix`
even though they use the same Python dependency files:

- `ai-engine.yml`
- `check-generated-models.yml`
- `pre_commit.yml`
- `sync_files_v2.yml`

All of these workflows use the same cache dependency inputs:

- `engine/pyproject.toml`
- `engine/uv.lock`

The workflow-specific suffixes caused separate cache entries to be
created for effectively identical dependency sets. This resulted in
unnecessary cache duplication and reduced cache reuse between workflows.

By removing the suffixes, these workflows can now share the same cache
when their dependency inputs and other cache key components match.

This change reduces redundant cache storage, improves cache hit
potential across CI workflows, and avoids repeatedly creating equivalent
caches under different names.

No functional application behavior is changed. The modification only
affects CI cache key generation and reuse.

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have run `task check` to verify linters, typechecks, and tests
pass
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

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

.github/workflows/ai-engine.yml

@@ -34,7 +34,6 @@ jobs:
           cache-dependency-glob: |
             engine/pyproject.toml
             engine/uv.lock
-          cache-suffix: ai-engine
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/check-generated-models.yml

@@ -42,7 +42,6 @@ jobs:
           cache-dependency-glob: |
             engine/pyproject.toml
             engine/uv.lock
-          cache-suffix: generated-models
 
       - name: Restore cache Gradle User Home
         if: inputs.use_shared_cache

.github/workflows/pre_commit.yml

@@ -31,7 +31,6 @@ jobs:
           cache-dependency-glob: |
             engine/pyproject.toml
             engine/uv.lock
-          cache-suffix: pre-commit
 
       - name: Install Task
         uses: go-task/setup-task@01a4adf9db2d14c1de7a560f09170b6e0df736aa # v2.1.0

.github/workflows/sync_files_v2.yml

@@ -59,7 +59,6 @@ jobs:
           cache-dependency-glob: |
             engine/pyproject.toml
             engine/uv.lock
-          cache-suffix: sync-files
 
       - name: Install Python dependencies
         run: |