docs: update README with full architecture, vision, and setup details

[g-k-s-03]

Closes #46

📝 Description

This PR updates the README.md file to include comprehensive documentation about the Ell-ena project — covering vision, architecture, setup steps, system components, and contribution guidelines.
It also clarifies the use of Deno’s --allow-env flag in backend setup instructions to prevent environment variable access issues.

Summary by CodeRabbit

• Documentation
  • Fixed duplicate step number in Getting Started.
  • Clarified running backend functions (require --allow-env) and listed required environment variables: VEXA_API_KEY, SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY.

[coderabbitai]

Walkthrough

Updated README.md to add environment configuration and backend setup instructions, including note to run Deno functions with the --allow-env flag and a list of required environment variables: VEXA_API_KEY, SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY.

Changes

Cohort / File(s)	Summary
README Environment Documentation README.md	Added "Environment Configuration" and backend setup notes under Getting Started; documented running Deno functions with --allow-env; listed required environment variables (VEXA_API_KEY, SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY) and minor formatting adjustments.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

• Verify the duplicate step numbering (e.g., "2. 2. Set up backend") is a formatting error.
• Confirm the environment variable names match runtime/config usage in the codebase.
• Ensure the Deno --allow-env instruction aligns with any existing developer/run scripts or CI settings.

Poem

🐰 README warmed by candlelight and care,

keys and flags laid open, clear and fair,
Deno hums softly, envs tucked in a row,
new contributors hop in, ready to go! 🥕✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The changes only address part of issue #46 - they document the --allow-env flag and environment variables but lack comprehensive environment setup instructions, troubleshooting tips, and actionable guidance mentioned in the issue.	Add full 'Environment Configuration' section with frontend .env setup instructions, backend configuration steps, troubleshooting tips, and clear guidance on finding API keys and Supabase credentials.
Title check	❓ Inconclusive	The PR title is broader than the actual changes (mentions architecture and vision) but the changeset only documents Deno setup with --allow-env flag.	Consider a more specific title like 'docs: clarify Deno --allow-env flag in backend setup' to better reflect the actual changes made.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Out of Scope Changes check	✅ Passed	The changes are narrowly scoped to documenting Deno environment setup and directly align with the backend setup aspect of issue #46.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 0770aa6 and 4c7936c.

📒 Files selected for processing (1)

• README.md (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• README.md

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Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between f5ff64c and 0770aa6.

📒 Files selected for processing (1)

• README.md (1 hunks)

🔇 Additional comments (1)

README.md (1)

147-151: Verification inconclusive: Issue #46 objectives not accessible in repository; comprehensive environment documentation already exists in BACKEND.md and FRONTEND.md.

The review comment references specific "PR objectives for linked issue #46," but I cannot locate these objectives in the repository—neither in git logs, commit messages, PR template, nor issue references.

However, I confirmed that comprehensive environment configuration documentation already exists:

• BACKEND.md contains "Configuring Environment Variables" (line 111+) with step-by-step setup for Gemini API key, Vexa API key, and explanation of client-safe vs server-only secrets
• FRONTEND.md includes "Set Up Environment Variables" section with .env setup instructions
• README.md properly directs users to these documents: "Follow instructions in BACKEND.md" and "Follow instructions in FRONTEND.md"

The changes add a specific --allow-env flag note for Deno functions, which is actionable guidance distinct from the comprehensive setup already documented elsewhere.

To resolve this review comment, manually verify issue #46 on GitHub to confirm whether the objectives specifically required a dedicated "Environment Configuration" section in README, or whether delegating to BACKEND.md and FRONTEND.md satisfies the requirements.