Feat: Implement Skill Synergy Combo Multiplier (#1173) - #1191

Summary

This PR introduces the "Skill Synergy" Combo Multiplier to address #1173. Previously, knowing highly synergistic skills like "React" and "Node.js" for a full-stack project only yielded a linear addition of points, failing to reward cohesive stack matches. This update adds a SYNERGY_MAP dictionary to the backend recommender containing predefined skill combinations. If a user possesses a specific combination of skills that forms a synergistic subset of the project's requirements, a max multiplier (e.g., 1.5) is applied to their skill score. Additionally, a new UI badge ("Synergy Match ✨") has been added to the frontend to visually highlight these perfect stack matches to the user.

Related Issue

Closes #1173

Type of Change

• Bug fix — resolves a broken behaviour
• Feature — adds new functionality
• Data — adds new projects to data/projects.json
• Documentation — updates docs, README, or code comments only
• Style — CSS or visual changes only, no logic change
• Refactor — restructures code without changing behaviour
• Test — adds or updates tests

What Was Changed

How to Test This PR

1. Clone this branch: git checkout feat/issue-1173-skill-synergy
2. Install dependencies: pip install -r requirements.txt
3. Run the app: python app.py
4. Enter React, Node in the skills input on the homepage and submit.
5. In the results, look for full-stack React+Node projects. You should see them boosted to the top of the list and marked with a "Synergy Match ✨" badge.
6. Run the tests: python tests/test_basic.py (or pytest tests/test_basic.py)

Expected test output:

27 passed, 0 failed out of 27 tests

Test Results

============================= test session starts ==============================
platform darwin -- Python 3.x.x, pytest-x.x.x, pluggy-x.x.x
rootdir: /Users/desireddymohithreddy/GSSOC2026DevPath/DevPathMRD
collected 27 items                                                             

tests/test_basic.py ...........................                          [100%]

============================== 27 passed in 0.12s ==============================

Self-Review Checklist

• I have read CONTRIBUTING.md and followed all guidelines
• My branch name follows the convention: feat/, fix/, docs/, data/, style/, test/
• I have run python tests/test_basic.py and all 27 tests pass
• I have run flake8 . locally and there are no errors
• I have not introduced any print() or console.log() debug statements
• Every new function I wrote has a docstring
• I have not modified files outside the scope of the linked issue
• If I changed the UI, I tested it at 375px (mobile) and 1280px (desktop)
• If I added a project to the dataset, it has all required JSON fields

Notes for Reviewer

None