Restructure component directories to group by environment tier

Problem
-------
The current flat naming convention (external-staging, internal-staging,
external-production, internal-production) makes it difficult to maintain
components that need independent staging and production configurations.

When a component requires a staging-specific base (e.g. different
resource sizing, different credentials, staging-only features), there
is no natural place for it. Recent PRs (#384, #369) worked around this
with ad-hoc conventions (staging-base/, production-base/) and
placeholder directories, because the flat structure assumes a single
shared base across all environments.

This also makes it hard to deploy to staging first and production
later — a common pattern for validating changes before they reach
production clusters.

Solution
--------
Group environment directories by tier first, then by cluster type:

  Before:                     After:
  external-staging/           staging/external/
  internal-staging/           staging/internal/
  external-production/        production/external/
  internal-production/        production/internal/

This enables a natural structure for tier-specific bases:

  components/prometheus/
  ├── staging/
  │   ├── base/           ← staging-specific config
  │   ├── external/
  │   └── internal/
  └── production/
      ├── base/           ← production-specific config
      ├── external/
      └── internal/

Components with a shared base across tiers keep their existing
base/ directory unchanged:

  components/smee/
  ├── base/               ← shared across staging and production
  ├── staging/
  │   └── external/
  └── production/
      └── external/

What changed
------------
- Renamed 46 environment directories across all 18 components
- Updated relative paths in 34 kustomization.yaml files (../base →
  ../../base, ../k-components → ../../k-components)
- Updated the 4 ArgoCD environment-patch.yaml files to match the
  new directory names

Verified that kustomize build output is byte-identical before and
after for all 75 overlays — this is a pure directory reorganization
with no functional change to any deployed manifest.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: oswcab

argo-cd-apps/overlays/external-production/environment-patch.yaml

@@ -1,4 +1,4 @@
 ---
 - op: replace
   path: /spec/generators/0/clusters/values/environment
-  value: external-production
+  value: production/external

argo-cd-apps/overlays/external-staging/environment-patch.yaml

@@ -1,4 +1,4 @@
 ---
 - op: replace
   path: /spec/generators/0/clusters/values/environment
-  value: external-staging
+  value: staging/external

argo-cd-apps/overlays/internal-production/environment-patch.yaml

@@ -1,4 +1,4 @@
 ---
 - op: replace
   path: /spec/generators/0/clusters/values/environment
-  value: internal-production
+  value: production/internal

argo-cd-apps/overlays/internal-staging/environment-patch.yaml

@@ -1,4 +1,4 @@
 ---
 - op: replace
   path: /spec/generators/0/clusters/values/environment
-  value: internal-staging
+  value: staging/internal