chore(go.mod): use lowercase module path

[ntlaletsi70]

What

Reverts the Go module path to github.com/blanketops/environments-api (lowercase), matching the actual GitHub remote.

Why

The module path had drifted to github.com/BlanketOps/environments-api (uppercase) during the recent org-migration cleanup; the canonical path is lowercase.

Domain

• environments
• events
• sources
• networks
• common
• Application / domain layer (no API surface change)
• CI / tooling / docs

API impact

• No API surface change
• v1alpha1 — free to change
• v1beta1 — backwards-compatible only, deprecations allowed
• v1 — breaking change (requires version bump + changelog entry + migration note)

Checklist

• mage verify passes locally (go build ./... confirmed)
• buf breaking reviewed (failures justified above if pre-v1) — N/A, this repo has no protobuf/buf
• Panic-free resolution — no panic() calls in resolution or domain layers
• Import paths use gen/go/blanketops/... for contract types — N/A, this repo uses Go-native kubebuilder types, not generated protobuf
• BlanketOps labels present where required (environments.blanketops.dev/*) — N/A, no controller/reconciliation code here
• Conditions written via core.SetCondition at each domain pipeline stage — N/A, no controller code in this repo
• Events emitted via core.EventRecorder for terminal outcomes — N/A, no controller code in this repo
• ESP-0001 updated if contract semantics changed — no contract semantics changed
• Commit messages follow Conventional Commits

Notes for reviewer

Several checklist items are inherited from the shared org template and don't apply to this repo (Go-types + kubebuilder CRDs, no protobuf/buf, no controller code) — marked N/A above rather than left silently unchecked.