docs: document all env vars with descriptions, examples, and required/optional markers

[devUnixx]

Closes AnnabelJoe#318

Changes

Updated apps/web/.env.example to fully document every environment variable:

• Added a legend at the top explaining [REQUIRED] vs [OPTIONAL]
• Split the three contract ID variables into separate entries, each with its own description of what the contract does
• Added [OPTIONAL] marker + fallback behaviour description to LOGTAIL_SOURCE_TOKEN (was missing)
• Added [OPTIONAL] marker + fallback behaviour description to CORS_ALLOWED_ORIGINS (was missing)
• Variables grouped by service: Supabase, Stellar/Soroban, Redis, Logging, CORS
• Safe example values provided for all variables

Acceptance criteria

• Every variable has an inline comment explaining its purpose
• Example values provided where safe
• Required vs optional variables clearly marked
• Variables grouped by service (Supabase, Redis, Stellar, Logging, CORS)

[github-actions]

✅ pnpm audit

4 vulnerabilities found
Severity: 4 moderate

[github-actions]

🔍 Vercel Preview Deployment

URL: Learn More: https://err.sh/vercel/no-credentials-found

Uses Stellar testnet contract addresses.

[github-actions]

✅ cargo audit

�[1m�[32m    Updating�[0m crates.io index
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�[1m�[36m      Adding�[0m arbitrary v1.3.2 �[1m�[33m(available: v1.4.2)�[0m
�[1m�[36m      Adding�[0m crypto-common v0.1.6 �[1m�[33m(available: v0.1.7)�[0m
�[1m�[36m      Adding�[0m derive_arbitrary v1.3.2 �[1m�[33m(available: v1.4.2)�[0m
�[1m�[36m      Adding�[0m soroban-builtin-sdk-macros v23.0.1 �[1m�[33m(available: v23.0.2)�[0m
�[1m�[36m      Adding�[0m soroban-env-common v23.0.1 �[1m�[33m(available: v23.0.2)�[0m
�[1m�[36m      Adding�[0m soroban-env-guest v23.0.1 �[1m�[33m(available: v23.0.2)�[0m
�[1m�[36m      Adding�[0m soroban-env-host v23.0.1 �[1m�[33m(available: v23.0.2)�[0m
�[1m�[36m      Adding�[0m soroban-env-macros v23.0.1 �[1m�[33m(available: v23.0.2)�[0m
�[1m�[36m      Adding�[0m soroban-sdk v23.5.3 �[1m�[33m(available: v25.3.0)�[0m
�[0m�[0m�[1m�[32m    Fetching�[0m advisory database from `https://github.com/RustSec/advisory-db.git`
�[0m�[0m�[1m�[32m      Loaded�[0m 1098 security advisories (from /home/runner/.cargo/advisory-db)
�[0m�[0m�[1m�[32m    Updating�[0m crates.io index
�[0m�[0m�[1m�[32m    Scanning�[0m Cargo.lock for vulnerabilities (192 crate dependencies)
�[0m�[0m�[1m�[33mCrate:    �[0m derivative
�[0m�[0m�[1m�[33mVersion:  �[0m 2.2.0
�[0m�[0m�[1m�[33mWarning:  �[0m unmaintained
�[0m�[0m�[1m�[33mTitle:    �[0m `derivative` is unmaintained; consider using an alternative
�[0m�[0m�[1m�[33mDate:     �[0m 2024-06-26
�[0m�[0m�[1m�[33mID:       �[0m RUSTSEC-2024-0388
�[0m�[0m�[1m�[33mURL:      �[0m https://rustsec.org/advisories/RUSTSEC-2024-0388
�[0m�[0m�[1m�[33mDependency tree:
�[0mderivative 2.2.0
├── ark-poly 0.4.2
│   └── ark-ec 0.4.2
│       ├── soroban-env-host 23.0.1
│       │   ├── soroban-sdk 23.5.3
│       │   │   ├── multisig-admin 1.0.0
│       │   │   ├── energy-token 1.0.0
│       │   │   ├── community-governance 1.0.0
│       │   │   └── audit-registry 1.0.0
│       │   └── soroban-ledger-snapshot 23.5.3
│       │       └── soroban-sdk 23.5.3
│       └── ark-bls12-381 0.4.0
│           └── soroban-env-host 23.0.1
├── ark-ff 0.4.2
│   ├── soroban-env-host 23.0.1
│   ├── ark-poly 0.4.2
│   ├── ark-ec 0.4.2
│   └── ark-bls12-381 0.4.0
└── ark-ec 0.4.2

�[0m�[0m�[1m�[33mCrate:    �[0m paste
�[0m�[0m�[1m�[33mVersion:  �[0m 1.0.15
�[0m�[0m�[1m�[33mWarning:  �[0m unmaintained
�[0m�[0m�[1m�[33mTitle:    �[0m paste - no longer maintained
�[0m�[0m�[1m�[33mDate:     �[0m 2024-10-07
�[0m�[0m�[1m�[33mID:       �[0m RUSTSEC-2024-0436
�[0m�[0m�[1m�[33mURL:      �[0m https://rustsec.org/advisories/RUSTSEC-2024-0436
�[0m�[0m�[1m�[33mDependency tree:
�[0mpaste 1.0.15
├── wasmi_core 0.13.0
│   └── soroban-wasmi 0.31.1-soroban.20.0.1
│       ├── soroban-env-host 23.0.1
│       │   ├── soroban-sdk 23.5.3
│       │   │   ├── multisig-admin 1.0.0
│       │   │   ├── energy-token 1.0.0
│       │   │   ├── community-governance 1.0.0
│       │   │   └── audit-registry 1.0.0
│       │   └── soroban-ledger-snapshot 23.5.3
│       │       └── soroban-sdk 23.5.3
│       └── soroban-env-common 23.0.1
│           ├── soroban-sdk-macros 23.5.3
│           │   └── soroban-sdk 23.5.3
│           ├── soroban-ledger-snapshot 23.5.3
│           ├── soroban-env-host 23.0.1
│           └── soroban-env-guest 23.0.1
│               └── soroban-sdk 23.5.3
└── ark-ff 0.4.2
    ├── soroban-env-host 23.0.1
    ├── ark-poly 0.4.2
    │   └── ark-ec 0.4.2
    │       ├── soroban-env-host 23.0.1
    │       └── ark-bls12-381 0.4.0
    │           └── soroban-env-host 23.0.1
    ├── ark-ec 0.4.2
    └── ark-bls12-381 0.4.0

�[0m�[0m�[1m�[33mwarning:�[0m 2 allowed warnings found