feat: copier update v0.9.0 — extraction docs, state tracking, architecture guides

Sync template from 29ac25b → v0.9.0 (29 template commits). Due to
template's _subdirectory migration, new files were manually rendered
rather than auto-merged by copier.

New files:
- .claude/CLAUDE.md + coding_philosophy.md (agent instructions)
- extract utils.py: SQLite state tracking for extraction runs
- extract/transform READMEs: architecture & pattern documentation
- infra/supervisor: systemd service + orchestration script
- Per-layer model READMEs (raw, staging, foundation, serving)

Also fixes copier-answers.yml (adds 4 feature toggles, removes stale
payment_provider key) and scopes CLAUDE.md gitignore to root only.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/CLAUDE.md

@@ -0,0 +1,106 @@
+# CLAUDE.md — Padelnomics
+
+This file tells Claude Code how to work in this repository.
+
+## Project Overview
+
+Padelnomics is a SaaS application built with Quart (async Python), HTMX, and SQLite.
+It includes a full data pipeline:
+
+```
+External APIs → extract → landing zone → SQLMesh transform → DuckDB → web app
+```
+
+**Packages** (uv workspace):
+- `web/` — Quart + HTMX web application (auth, billing, dashboard)
+- `extract/padelnomics_extract/` — data extraction to local landing zone
+- `transform/sqlmesh_padelnomics/` — 4-layer SQL transformation (raw → staging → foundation → serving)
+- `src/padelnomics/` — CLI utilities, export_serving helper
+
+## Skills: invoke these for domain tasks
+
+### Working on extraction or transformation?
+
+Use the **`data-engineer`** skill for:
+- Designing or reviewing SQLMesh model logic
+- Adding a new data source (extract + raw + staging models)
+- Performance tuning DuckDB queries
+- Data modeling decisions (dimensions, facts, aggregates)
+- Understanding the 4-layer architecture
+
+```
+/data-engineer  (or ask Claude to invoke it)
+```
+
+### Working on the web app UI or frontend?
+
+Use the **`frontend-design`** skill for UI components, templates, or dashboard layouts.
+
+### Working on payments or subscriptions?
+
+Use the **`paddle-integration`** skill for billing, webhooks, and subscription logic.
+
+## Key commands
+
+```bash
+# Install all dependencies
+uv sync --all-packages
+
+# Lint & format
+ruff check .
+ruff format .
+
+# Run tests
+uv run pytest tests/ -v
+
+# Dev server
+./scripts/dev_run.sh
+
+# Extract data
+LANDING_DIR=data/landing uv run extract
+
+# SQLMesh plan + run (from repo root)
+uv run sqlmesh -p transform/sqlmesh_padelnomics plan
+uv run sqlmesh -p transform/sqlmesh_padelnomics plan prod
+
+# Export serving tables (run after SQLMesh)
+DUCKDB_PATH=local.duckdb SERVING_DUCKDB_PATH=analytics.duckdb \
+    uv run python -m padelnomics.export_serving
+```
+
+## Architecture documentation
+
+| Topic | File |
+|-------|------|
+| Extraction patterns, state tracking, adding new sources | `extract/padelnomics_extract/README.md` |
+| 4-layer SQLMesh architecture, materialization strategy | `transform/sqlmesh_padelnomics/README.md` |
+| Two-file DuckDB architecture (SQLMesh lock isolation) | `src/padelnomics/export_serving.py` docstring |
+
+## Pipeline data flow
+
+```
+data/landing/
+  └── padelnomics/{year}/{etag}.csv.gz   ← extraction output
+
+local.duckdb                ← SQLMesh exclusive (raw → staging → foundation → serving)
+
+analytics.duckdb            ← serving tables only, web app read-only
+  └── serving.*             ← atomically replaced by export_serving.py
+```
+
+## Environment variables
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `LANDING_DIR` | `data/landing` | Landing zone root (extraction writes here) |
+| `DUCKDB_PATH` | `local.duckdb` | SQLMesh pipeline DB (exclusive write) |
+| `SERVING_DUCKDB_PATH` | `analytics.duckdb` | Read-only DB for web app |
+
+## Coding philosophy
+
+- **Simple and procedural** — functions over classes, no "Manager" patterns
+- **Idempotent operations** — running twice produces the same result
+- **Explicit assertions** — assert preconditions at function boundaries
+- **Bounded operations** — set timeouts, page limits, buffer sizes
+
+Read `coding_philosophy.md` (if present) for the full guide.