Automate versioning + changelog on every deploy (v0.2.0)

- changelog.json is now the single source of truth; version.py reads it.
- release.py: one command to bump version + prepend a changelog entry + regen
  CHANGELOG.md. Dogfooded to cut 0.2.0.
- repo CLAUDE.md documents the MANDATORY 'cut a release on every deploy' rule
  + deploy/secrets conventions, so it applies to anyone who pulls the repo.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

release.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+"""Cut a release for Moon Household Budget.
+
+Usage:
+    python release.py <version> "<change 1>" "<change 2>" ... \\
+        [--title "Short title"] [--date YYYY-MM-DD]
+
+Prepends a new entry to changelog.json (the single source of truth that drives
+__version__, the footer version chip, and the /changelog page) and regenerates
+CHANGELOG.md to match.
+
+Versioning: semver-ish — bump the patch (0.1.0 -> 0.1.1) for fixes, the minor
+(0.1.0 -> 0.2.0) for new features. Run this for EVERY deploy (see CLAUDE.md).
+"""
+import json
+import os
+import sys
+from datetime import date
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+CHANGELOG_JSON = os.path.join(HERE, "changelog.json")
+CHANGELOG_MD = os.path.join(HERE, "CHANGELOG.md")
+
+
+def load():
+    try:
+        with open(CHANGELOG_JSON) as f:
+            return json.load(f)
+    except (OSError, json.JSONDecodeError):
+        return []
+
+
+def render_md(data):
+    lines = [
+        "# Changelog",
+        "",
+        "All notable changes to Moon Household Budget. Newest first.",
+        "Generated from changelog.json by release.py — do not edit by hand.",
+        "",
+    ]
+    for rel in data:
+        head = f"## {rel['version']} — {rel.get('date', '')}"
+        if rel.get("title"):
+            head += f" — {rel['title']}"
+        lines += [head, ""]
+        lines += [f"- {c}" for c in rel.get("changes", [])]
+        lines.append("")
+    return "\n".join(lines)
+
+
+def main(argv):
+    if len(argv) < 2:
+        print(__doc__)
+        return 1
+
+    version = argv[1]
+    title, rel_date, changes = "", date.today().isoformat(), []
+    i = 2
+    while i < len(argv):
+        if argv[i] == "--title" and i + 1 < len(argv):
+            title = argv[i + 1]; i += 2
+        elif argv[i] == "--date" and i + 1 < len(argv):
+            rel_date = argv[i + 1]; i += 2
+        else:
+            changes.append(argv[i]); i += 1
+
+    if not changes:
+        print("error: provide at least one change bullet")
+        return 1
+
+    data = load()
+    if data and data[0].get("version") == version:
+        print(f"error: version {version} is already the latest entry")
+        return 1
+
+    entry = {"version": version, "date": rel_date}
+    if title:
+        entry["title"] = title
+    entry["changes"] = changes
+    data.insert(0, entry)
+
+    with open(CHANGELOG_JSON, "w") as f:
+        json.dump(data, f, indent=2)
+        f.write("\n")
+    with open(CHANGELOG_MD, "w") as f:
+        f.write(render_md(data))
+
+    print(f"released v{version} ({rel_date}) with {len(changes)} change(s)")
+    print("  -> changelog.json + CHANGELOG.md updated. Now commit + deploy.")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))