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>

version.py

@@ -1,26 +1,18 @@
-"""App version + changelog.
+"""App version + changelog, sourced from changelog.json (single source of truth).
 
-To cut a release: bump __version__ and prepend a new entry to CHANGELOG
-(newest first), then keep CHANGELOG.md in sync. The version chip in the footer
-links to /changelog, which renders these entries.
+Cut releases with:  python release.py <version> "<what changed>" ...
+That prepends an entry to changelog.json and regenerates CHANGELOG.md. The
+footer version chip and the /changelog page read from here automatically.
 """
-__version__ = "0.1.0"
+import json
+import os
 
-# Newest first. Each release lists what's new in plain language.
-CHANGELOG = [
-    {
-        "version": "0.1.0",
-        "date": "2026-06-06",
-        "title": "First tracked release",
-        "changes": [
-            "Crash-safe data storage — saves are now atomic and a corrupted file can no longer take the app down.",
-            "Transactions moved to a SQLite database: faster, and safe when edited from two tabs at once. Existing transactions were migrated automatically.",
-            "New Settings page (⚙️) to store your Gmail login and reminder preferences securely — no passwords in the code anymore.",
-            "Suggestions & feedback (💡) is now reachable from every page; what you send becomes a tracked issue.",
-            "Bill email reminders now use the Gmail login from Settings.",
-            "Automatic daily backups of all your data (local for now; Backblaze cloud once a bucket is set up).",
-            "Fixed the Monthly view crashing on the budget total.",
-            "Added this version number and changelog.",
-        ],
-    },
-]
+_CHANGELOG_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), "changelog.json")
+
+try:
+    with open(_CHANGELOG_PATH) as f:
+        CHANGELOG = json.load(f)
+except (OSError, json.JSONDecodeError):
+    CHANGELOG = []
+
+__version__ = CHANGELOG[0]["version"] if CHANGELOG else "0.0.0"