chore(deploy): add .railwayignore — slim the Railway upload to source only

The MCP/CLI tarball upload was 294MB (413 Payload Too Large) because it swept in
node_modules (542M), the clients/ submodules (341M LFS PDFs + corpus), and .git.
The Dockerfile installs deps and builds inside the image, so the build context
only needs source. Excludes node_modules/dist/.git/clients/secrets/scratch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018UYTYu4MAFZ7iyr2VTo2kq

Author: mpstaton

.railwayignore

@@ -0,0 +1,21 @@
+# Keep the Railway upload tarball to SOURCE only — the Dockerfile installs deps
+# and builds inside the image, so none of this belongs in the build context.
+.git
+node_modules
+**/node_modules
+**/dist
+**/.astro
+**/.turbo
+
+# Client submodules (corpus + LFS PDFs) — only content-ingest's volume needs
+# these, never a frontend/service build.
+clients
+
+# Local secrets + scratch — build args come from Railway service variables.
+.env
+.env.*
+*.log
+history.txt
+scratchpad
+ogimage-archive
+ideogram-candidates