feat(deployment)!: move deployment.env to deployment.gitea.env and add deployment.enabled

The `deployment` dict mixes values that apply to the Deployment object itself (`annotations`, `labels`,
`affinity`, `terminationGracePeriodSeconds`) with values that apply to a single container. `deployment.env` was
the only container-scoped key, which made it unclear which container it targets once further containers get
their own configuration.

Grouping container-scoped values under `deployment.gitea` establishes a per-container namespace and leaves room
for sibling sections without another breaking rename later. The value ordering in `values.yaml` is aligned with
the chart conventions (`enabled`, `annotations`, `labels` first).

`deployment.enabled` is introduced and wired up in the template so the Deployment can be skipped entirely. This
allows the chart to be used for rendering only the surrounding resources, e.g. when the workload itself is
managed elsewhere.

A deprecation check is added so that existing installations fail fast with an actionable error message instead
of silently dropping their environment variables, which would otherwise surface as hard-to-debug runtime
misconfiguration.

Unit tests cover the disabled Deployment, the propagation of `deployment.gitea.env` into all init containers and
the Gitea container, and the deprecation checks for `affinity` and `deployment.env`.

BREAKING CHANGE: `deployment.env` no longer exists. Use `deployment.gitea.env` instead. Installations that
still set `deployment.env` will fail unless `checkDeprecation` is set to `false`.

Co-authored-by: Copilot <copilot@github.com>

unittests/helm/deployment/deprecations.yaml

@@ -0,0 +1,44 @@
+suite: deprecation template (deployment)
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/deprecation.yaml
+tests:
+  - it: renders nothing with the default values
+    asserts:
+      - hasDocuments:
+          count: 0
+  - it: fails when the removed `affinity` value is set
+    set:
+      affinity:
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+              - matchExpressions:
+                  - key: kubernetes.io/os
+                    operator: In
+                    values:
+                      - linux
+    asserts:
+      - failedTemplate:
+          errorMessage: "`affinity` does no longer exist. Please refer to the changelog and configure `deployment.affinity` instead."
+  - it: fails when the removed `deployment.env` value is set
+    set:
+      deployment.env:
+        - name: VARIABLE
+          value: my-value
+    asserts:
+      - failedTemplate:
+          errorMessage: "`deployment.env` does no longer exist. Please refer to the changelog and configure `deployment.gitea.env` instead."
+  - it: skips the deprecation checks when `checkDeprecation` is disabled
+    set:
+      checkDeprecation: false
+      affinity:
+        nodeAffinity: {}
+      deployment.env:
+        - name: VARIABLE
+          value: my-value
+    asserts:
+      - hasDocuments:
+          count: 0