docs: add BrainWave analysis report

[kushagra-nigam-java]

Motivation

• Provide a concise, repository-rooted analysis of BrainWave's codebase and the locally rendered website to guide next steps for offline robustness, i18n, and content/workflow improvements.

Description

• Add ANALYSIS.md containing an assessment of architecture, offline/local-storage model, navigation, internationalization, rendered-site UX, risks, and a prioritized recommendation roadmap (P0/P1/P2).
• The file documents specific issues observed during a local run (e.g., localization coverage gaps, subject-filter key mismatch risk, lack of PWA/service-worker caching) and suggests mitigations.
• This is documentation-only and does not change runtime code or app behavior.

Testing

• Ran the dev server with npm run dev -- --hostname 0.0.0.0 --port 3000 and the app started successfully.
• Captured a homepage screenshot via the Playwright script (mcp__browser_tools__run_playwright_script) which produced artifacts/brainwave-home.png successfully for UI verification.
• Ran npm run lint which failed due to the repository lacking an ESLint v9 flat eslint.config.* file (failure documented in the analysis).

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Codex Task