grafana: deploy Grafana instance, datasource and dashboards (#238)

## Why
Deploys Grafana in-cluster (observability project) via the grafana-operator, mirroring the puppet Grafana but modernised — **CNPG** for state, **Authentik OIDC** for auth — and ports the live datasource + dashboards in as CRs.

Depends on: grafana-operator (#235, merged), grafana schemas (#236, merged), Authentik OIDC (terraform-authentik #2), Vault seeds (done), and `^grafana/` image proxy (terraform-artifactapi #5).

## Changes (`apps/base/grafana`)
- **CNPG** postgres Cluster + rw Pooler (db `grafana`); **VaultAuth** + **VaultStaticSecrets** pulling `postgres`/`oauth` credentials from `kv/kubernetes/namespace/grafana/default/*`.
- **Grafana CR**: postgres backend via the pooler; Authentik `generic_oauth` (client id/secret from the Vault-synced secret, openid/email/profile scopes, group→role mapping); `root_url` grafana.k8s.syd1.au.unkin.net.
- **1 GrafanaDatasource** — k8s VictoriaMetrics via the operator `vmselect-main` service; reuses the previous default datasource uid so the imported dashboards resolve unedited.
- **13 GrafanaDashboards** (gzipJson) exported from the current grafana.
- **Gateway API** (traefik-internal) + HTTPRoute for grafana.k8s.syd1.au.unkin.net.
- Registered in the observability ApplicationSet + project.

## Review notes
- OAuth `role_attribute_path` maps Authentik group `grafana-admins` → Admin, else Viewer — **confirm the group name**.
- `database.ssl_mode: require` against the CNPG pooler — adjust if the pooler isn't serving TLS.
- The `VictoriaLogs - cluster` dashboard has no in-cluster logs datasource yet (no VictoriaLogs in k8s) — included for completeness, will be empty until one exists.
- `make kubeconform` clean (24 resources, validated against the strict grafana schemas).

Reviewed-on: #238
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/grafana/grafana.yaml

@@ -0,0 +1,60 @@
+---
+apiVersion: grafana.integreatly.org/v1beta1
+kind: Grafana
+metadata:
+  name: grafana
+  namespace: grafana
+  labels:
+    dashboards: "grafana"
+spec:
+  deployment:
+    spec:
+      template:
+        spec:
+          containers:
+            - name: grafana
+              env:
+                # DB password + OAuth client secret injected from the
+                # Vault-synced secrets (GF_ env overrides grafana.ini).
+                - name: GF_DATABASE_PASSWORD
+                  valueFrom:
+                    secretKeyRef:
+                      name: postgres-credentials
+                      key: password
+                - name: GF_AUTH_GENERIC_OAUTH_CLIENT_SECRET
+                  valueFrom:
+                    secretKeyRef:
+                      name: oauth-credentials
+                      key: client_secret
+              resources:
+                requests:
+                  cpu: 100m
+                  memory: 256Mi
+                limits:
+                  cpu: "1"
+                  memory: 1Gi
+  config:
+    server:
+      root_url: "https://grafana.k8s.syd1.au.unkin.net"
+    database:
+      type: "postgres"
+      host: "postgres-pooler-rw.grafana.svc.cluster.local:5432"
+      name: "grafana"
+      user: "grafana"
+      ssl_mode: "require"
+    auth:
+      disable_login_form: "false"
+      oauth_auto_login: "false"
+    "auth.generic_oauth":
+      enabled: "true"
+      name: "Authentik"
+      allow_sign_up: "true"
+      use_pkce: "true"
+      client_id: "grafana"
+      scopes: "openid email profile"
+      auth_url: "https://identity.unkin.net/application/o/authorize/"
+      token_url: "https://identity.unkin.net/application/o/token/"
+      api_url: "https://identity.unkin.net/application/o/userinfo/"
+      # Authentik groups -> Grafana roles (adjust group name as needed).
+      role_attribute_path: "contains(groups[*], 'grafana-admins') && 'Admin' || 'Viewer'"
+      role_attribute_strict: "false"