Add insight cells and CPI-adjusted revenue analysis to JFC notebook

[dayview]

Summary

• Adds a "Key Insight" markdown cell after each of the four existing chart sections (Q1–Q4) in jollibee-profitability-growth-analysis/jfc_data_preparation.ipynb, giving a plain-language interpretation of what each chart shows instead of leaving charts to speak for themselves.
• Adds a new Q5 section that deflates annual consolidated revenue by the food CPI index (rebased to 2021) to compare nominal vs. real (inflation-adjusted) revenue growth — this is the first place in the notebook that actually uses the food_cpi_ph column, which was collected but previously unused.
• Q3's insight cell flags a data-quality observation (the store count distribution is heavily right-skewed, with a few quarters sitting suspiciously close to the global store count) rather than asserting a clean growth narrative not supported by the numbers.

Notes for reviewer

• The source CSV (infom_data.csv) isn't checked into the repo, so the new Q5 cells haven't been executed — please run the notebook top-to-bottom once to confirm the CPI-adjustment logic (groupby('year')['food_cpi_ph'].mean() reused against the existing annual_rev dict) produces sensible output before merging.

Test plan

• Run the notebook top-to-bottom locally with infom_data.csv present
• Confirm Q5 nominal vs. real growth chart renders and numbers look reasonable
• Spot-check the Q3 store-count caveat against the original JFC press releases

🤖 Generated with Claude Code