ci: modernize GitHub Actions workflows, labelers, and issue templates to production grade

[santusht06]

Summary [required]

This PR modernizes and hardens the GitHub Actions CI/CD pipeline, PR/issue automated triage workflows, and labeler configuration for DevPath:

1. CI Pipeline Hardening (python-app.yml): Adds pip caching via actions/setup-python@v7, introduces blocking syntax/fatal error checks (E9,F63,F7,F82), undefined variable checks (F821), advisory style checks, and verbose test execution with pytest.
2. Workflow Streamlining & Permissions:
   • Consolidates PR title regex and file-based labeling across .github/workflows/auto-label-prs.yml, .github/workflows/auto-file-labels.yml, and .github/labeler.yml.
   • Cleans up issue creation triage in .github/workflows/issue-management.yml to safely auto-assign creators and attach program labels without failing on non-member permissions.
   • De-duplicates redundant issue labeling logic (auto-label-issues.yml).
3. Issue Template Placement: Moves config.yml under .github/ISSUE_TEMPLATE/ so GitHub correctly recognizes blank issue restrictions and contact links.
4. Stale Automation (stale.yml): Introduces a scheduled maintenance workflow (actions/stale@v9) to automatically triage inactive issues and pull requests while exempting security, pinned, and in-progress items.
5. Test Suite Hygiene (tests/test_admin_csrf.py): Wraps CSRF enablement mutations in try...finally blocks to guarantee test state isolation and prevent state leakage across test runs.

Type of Change [required]

• Bug fix — resolves broken/redundant workflow behavior and test state leaks
• Refactor — restructures and modernizes CI/CD pipelines
• Test — hardens CSRF test teardown

What Was Changed [required]

File	Change made
.github/workflows/python-app.yml	Added pip caching, blocking syntax checks (E9,F63,F7,F82), and verbose pytest runner
.github/workflows/auto-label-prs.yml	Modernized PR title categorization regex and label mappings
.github/workflows/auto-file-labels.yml	Updated file labeler trigger and permissions
.github/workflows/issue-management.yml	Safe creator auto-assignment and GSSoC-2026 label assignment with error handling
.github/workflows/auto-label-issues.yml	Removed redundant duplicate workflow
.github/workflows/stale.yml	Added daily scheduled workflow to triage inactive issues/PRs
.github/labeler.yml	Added comprehensive file matching patterns across src/, data/, docs/, and tests/
.github/ISSUE_TEMPLATE/config.yml	Relocated into ISSUE_TEMPLATE/ for proper GitHub issue form rendering
.github/ISSUE_TEMPLATE/data_contribution.yml	Refined default label configuration
.github/workflows/deploy.yml	Added explicit permissions configuration
tests/test_admin_csrf.py	Wrapped WTF_CSRF_ENABLED test configurations in try...finally teardowns

How to Test This PR [required]

1. Clone this branch: git checkout fix/cicd-pipeline-and-workflow-modernization
2. Install dependencies: pip install -r requirements.txt && pip install -r requirements-dev.txt
3. Run tests with pytest: PYTHONPATH=src pytest -v
4. Run syntax and fatal error checks: flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics

Expected test output:

664 passed, 4 skipped in 5.70s

Test Results [required]

======================== 664 passed, 4 skipped in 5.70s ========================

Self-Review Checklist [required]

• I have read CONTRIBUTING.md and followed all guidelines
• My branch name follows the convention: fix/
• All test suites pass (664 passed)
• No print() or console.log() debug statements introduced
• Tested locally on Python 3.11 / 3.12

[vercel]

@santusht06 is attempting to deploy a commit to the komalsony234-1530's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

Thank you for submitting your first pull request to DevPath.

Before review:

• Complete the PR template fully
• Ensure all tests pass
• Link your PR to an issue
• Keep changes scoped to the issue

A maintainer will review your contribution soon.