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>

changelog.json

@@ -0,0 +1,26 @@
+[
+  {
+    "version": "0.2.0",
+    "date": "2026-06-06",
+    "title": "Automatic version + changelog on every update",
+    "changes": [
+      "Every app update now automatically bumps the version and adds a 'What's New' entry, so you always see what changed.",
+      "Added a one-command release tool and wrote the process into the project so any future change stays documented."
+    ]
+  },
+  {
+    "version": "0.1.0",
+    "date": "2026-06-06",
+    "title": "First tracked release",
+    "changes": [
+      "Crash-safe data storage \u2014 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 (\u2699\ufe0f) to store your Gmail login and reminder preferences securely \u2014 no passwords in the code anymore.",
+      "Suggestions & feedback (\ud83d\udca1) 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."
+    ]
+  }
+]