Initialize eng-pad-server with project documentation

- README.md: project overview, quick start, build commands
- CLAUDE.md: AI dev context, source tree, key conventions
- ARCHITECTURE.md: full system spec covering data model, auth
  (password + FIDO2/U2F), gRPC sync API, REST API, SVG/JPG/PDF
  rendering, web UI, configuration, deployment, security
- PROJECT_PLAN.md: 11 phases with discrete checkboxable steps
- PROGRESS.md: decision log and completion tracking

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -0,0 +1,53 @@
+eng-pad-server
+==============
+
+Read-only sync and web viewer for [eng-pad](https://git.wntrmute.dev/kyle/eng-pad)
+engineering notebooks.
+
+The Android app pushes complete notebooks to this server via gRPC. The
+server stores them and serves read-only views through a web UI with
+SVG rendering. Shareable links allow unauthenticated access to specific
+notebooks.
+
+## Features
+
+- **gRPC sync**: receive notebook data from the Android app over TLS
+- **Web viewer**: browse notebooks, view pages as SVG, export JPG/PDF
+- **Authentication**: password (Argon2id) + FIDO2/U2F security keys
+- **Shareable links**: token-based URLs with optional expiry
+
+## Quick Start
+
+```bash
+# Build
+make eng-pad-server
+
+# Generate example config
+cp eng-pad-server.toml.example /srv/eng-pad-server/eng-pad-server.toml
+# Edit configuration (TLS certs, database path, etc.)
+
+# Initialize (creates database, prompts for admin user)
+./eng-pad-server init
+
+# Run
+./eng-pad-server server
+```
+
+## Build
+
+```bash
+make all          # vet → lint → test → build
+make test         # run tests
+make lint         # golangci-lint
+make proto        # regenerate gRPC code from .proto files
+make proto-lint   # buf lint + breaking change detection
+```
+
+## Documentation
+
+- [ARCHITECTURE.md](ARCHITECTURE.md) — full system specification
+- [CLAUDE.md](CLAUDE.md) — AI development context
+
+## License
+
+Private. All rights reserved.