feat(podcasts+ops): Apple launcher-scheme feeds + visible build stamp

Apple scheme normalization (follow-up to the Scribl discussion): Add
Feed accepts the launcher spellings podcast pages ship next to plain
RSS — itpc://, podcasts://, feed:// — and rewrites them to the https
feed URL they wrap (scheme match case-insensitive). http stays and the
guard still rejects it. Unit-pinned.

Build stamp (stale-container drift guard): the 2026-10-29 podcast
session lost an hour to a container running a build that predated the
feature. version.Commit rides ldflags from a GIT_COMMIT build arg; the
dev compose passes git rev-parse --short HEAD via the Makefile; the
app logs 'Bookhoard <ver> (commit <hash>)' at boot and /api/health
reports it — the UI and the repo can no longer silently diverge.

Dockerfile

@@ -41,12 +41,14 @@ RUN npm run build:ts
 # Declared after `COPY . .` so a version bump only invalidates this layer.
 # The release workflow passes the git tag, e.g. APP_VERSION=v1.5.
 ARG APP_VERSION=dev
+# Short commit hash of the built source (stale-container drift guard).
+ARG GIT_COMMIT=none
 
 # Build Go binary (cached unless Go files or generated code changes)
 RUN --mount=type=cache,target=/root/go/pkg/mod \
   --mount=type=cache,target=/root/.cache/go-build \
   CGO_ENABLED=0 GOOS=linux go build -installsuffix cgo \
-  -ldflags "-X bookhoard/internal/version.Version=${APP_VERSION}" \
+  -ldflags "-X bookhoard/internal/version.Version=${APP_VERSION} -X bookhoard/internal/version.Commit=${GIT_COMMIT}" \
   -o main ./cmd/server
 
 # Materialize the Go module cache into an image layer so the test-runner