refactor(k8s): organize Helm templates into common/aws/onprem

Group the chart's templates by where they apply so the layout makes the
deployment surface obvious at a glance:

  templates/common/  resources every deployment needs (services, gateway,
                     postgres/lakefs/lakekeeper, computing-unit pool, RBAC)
  templates/onprem/  self-hosted-only resources (in-cluster MinIO)
  templates/aws/     AWS/EKS-only resources (added in later PRs; placeholder)

Helm renders templates/** recursively, so this is purely organizational:
`helm template` output is byte-identical to before the move (verified, modulo
the chart's pre-existing per-render random LakeFS keys). A templates/README.md
documents the convention and a .helmignore keeps the doc and .gitkeep
placeholder from being loaded as manifests.

Also bring values-development.yaml back in line with values.yaml (the ground
truth), which had drifted:
  - image source: docker.io/apache + 1.3.0-incubating-SNAPSHOT (was the stale
    ghcr.io/apache + latest), so both value files pull from the same place;
  - add the AUTH_JWT_SECRET entry to texeraEnvVars. values.yaml has it but the
    dev profile omitted it, so the computing-unit manager started without the
    secret and k8s computing-unit creation crashed with NoSuchElementException
    (None.get) in ComputingUnitManagingResource. Adding it (same dev-only
    default as values.yaml) makes CU creation work under the dev profile.

No behavior change to the default (on-prem) install.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: aicam

bin/k8s/.helmignore

@@ -0,0 +1,17 @@
+# Patterns to ignore when building Helm packages.
+# Operating system / editor files
+.DS_Store
+*.swp
+*.bak
+*.tmp
+*.orig
+*~
+# Version control directories
+.git/
+.gitignore
+# Documentation kept alongside the chart for humans, not rendered as manifests.
+# Markdown under templates/ (e.g. the common/aws/onprem layout guide) must be
+# ignored so Helm does not try to load it as a Kubernetes manifest.
+*.md
+# git placeholders must not be loaded by Helm as manifests
+.gitkeep

bin/k8s/templates/README.md

@@ -0,0 +1,2 @@
+# Placeholder so the (initially empty) aws/ template folder is tracked in git.
+# AWS-only, value-gated templates are added by later PRs in the AWS/EKS series.