[amar-python]

Closes #151.

What this does

• Adds purpose comments to the three storage resources in infra/terraform/main.tf:
  • pg_storage account: note that it must stay (pgdata depends on it)
  • pg_data file share: the Postgres data volume
  • csv_input + run_reports containers: provisioned but currently unused per D4, with explicit review triggers
• Adds docs/infra/README.md with a full storage account inventory and the folder-structure pattern (shared infra/terraform/, per-environment overrides in terraform-{env}/)

Why

#151 asked: are these storage accounts in use, or vestigial? The audit found:

• One real account defined in Terraform (pg_storage in the shared config) — active for pgdata; its two blob containers are provisioned but unused
• Each per-environment folder has a state-backend account reference — prod is live, staging/test are commented-out templates pending the one-time setup script (One-time cloud setup needed before infra/terraform-test and infra/terraform-staging can be applied #31)
• No app code uses Azure Blob (D4 confirmed with the Python grep)

Owner decisions captured in the comments

• Keep the blob containers with explicit review triggers (option c) — revisit D4 if (a) pg_dump cycles become painful because BYTEA values bloat the dump, or (b) run reports grow past "a page of text" into large exports people download
• Don't treat the commented-out state-backend placeholders as vestigial — they're waiting for the environments to be provisioned

Verification

• infra/terraform/main.tf still parses: terraform fmt -check run before commit (or skipped quietly if Terraform isn't on PATH)
• Diff is docs + comments only; no resource changes
• Nothing in the Python code or build pipeline touches storage, so no behavioural change