ytdlp-web-player: new chart with an optional oauth2-proxy subchart (1.0.0+upv1.2.0)

Deploys matszwe02/ytdlp_web_player, a Flask app that fetches videos with
yt-dlp, transcodes them with ffmpeg and serves them as HLS. It ships no
authentication of any kind, so the chart carries a preconfigured oauth2-proxy
as an optional subchart, in the data path in front of the app.

This is the first chart in the repo with a dependency, so the rule "charts
have no dependencies" falls here. It is replaced in CLAUDE.md and README.md by
a bar: a dependency has to be optional and off by default, upstream's chart is
consumed as it comes (documented where it falls short of our conventions,
never patched), and the price is written down - above all that a subchart is
invisible to everything downstream watching Helm release versions, so a new
proxy release only reaches a cluster when this chart is republished.

CI learns the dependency in five places, not the three the plan expected:
helm lint, package, template and install all exit 1 while charts/ is unfilled,
so ci/helm-dependencies.sh runs before lint and package in validate-charts.yml,
before package in publish-helm-chart.yml, and inside run-install-test.sh,
run-trivy-config.sh and run-quantity-render-test.sh - the last of which renders
every chart on every PR and would have gone red first.

Notable chart decisions, each measured rather than assumed:

- The image has no USER and runs as root by default, but not by necessity: it
  runs under an arbitrary uid with readOnlyRootFilesystem and the full
  hardening baseline. Only the pinned uid is a deviation, and it is documented.
- Two emptyDirs, each justified separately. /data holds the video cache
  (DATA_PATH). /tmp is NOT mounted - measured across metadata extraction, HLS
  transcoding, sprite generation and audio extraction, the image never writes
  there. What it does write is $HOME/.cache, so /cache is mounted with HOME and
  XDG_CACHE_HOME pointed at it; without it yt-dlp re-downloads its JavaScript
  challenge-solver from github.com on every extraction.
- The proxy is wired through config.configFile, the only value the subchart
  passes through tpl - config.upstreams is emitted with toJson and would carry
  a literal {{ .Release.Name }} into the manifest.
- Rendering aborts when this chart's Ingress and the proxy's claim the same
  host: ingress-nginx rejects the second one and a Fleet bundle then sits in
  ErrApplied until forceSyncGeneration is bumped.

Fixes #214

.gitignore

@@ -1,6 +1,29 @@
 ### Example user template template
 ### Example user template
 
+# Fetched Helm subchart archives and the lock file that records them (#214).
+#
+# Neither is committed, on purpose. The .tgz is a third-party binary that would
+# land in every diff of a dependency update and be reviewed by nobody; CI
+# fetches it with ci/helm-dependencies.sh before every lint, package, render
+# and install.
+#
+# The lock is left out for a concrete reason rather than by omission: Renovate
+# rewrites the version in Chart.yaml and cannot regenerate Chart.lock, so a
+# committed lock would be stale on arrival - and `helm dependency build`, the
+# only command that would benefit from it, fails outright when lock and
+# Chart.yaml disagree. Every dependency PR would come in red. `helm dependency
+# update` resolves from Chart.yaml instead and writes the lock itself.
+#
+# What is given up with it: the digest pinning a committed lock would provide.
+# The version range in Chart.yaml is an exact version, so what moves is only
+# what the upstream repo serves under that version.
+*/charts/*.tgz
+*/Chart.lock
+
+# Local helm package output.
+*.tgz
+
 # IntelliJ project files
 .idea
 *.iml