Add Secrets Manager resolution to probod-bootstrap

Introduce a Resolver that owns env lookup and typed parsing for
probod-bootstrap. Env values prefixed with aws://<secret-id> are
fetched from AWS Secrets Manager (plaintext SecretString); each
secret ID is cached per run. Builder now takes a Resolver only.

Prefix every probod-bootstrap input with PROBOD_ so bootstrap config
does not collide with unrelated process environment (for example
AWS_* used by other tooling). Secrets Manager authentication uses
the standard AWS SDK default chain (AWS_REGION, IAM role, profile);
PROBOD_AWS_* vars configure S3 in the generated config only.

Update Helm deployment env names, GNUmakefile dev-config, Lima
provision, e2e testutil, compose.prod.yaml, and docs.

Deployments must rename bootstrap env vars to PROBOD_* (e.g.
AUTH_COOKIE_SECRET → PROBOD_AUTH_COOKIE_SECRET).

BREAKING CHANGE: all env vars are now prefixed by `PROBOD_`.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

entrypoint.sh

@@ -5,6 +5,7 @@ set -e
 CONFIG_FILE="${CONFIG_FILE:-/etc/probod/config.yml}"
 
 # If bootstrap env vars are set, always (re)generate the config from them.
+# This includes literal values and aws:// Secrets Manager references.
 # This ensures that updated env vars take effect even when a stale config
 # file exists on a persistent volume.  When no env vars are present, fall
 # back to an existing config file (e.g., mounted from a ConfigMap).