Add version chip (v0.1.0) + changelog

- version.py: __version__ = 0.1.0 + structured CHANGELOG (newest first).
- footer version chip on every page (base.html) links to /changelog.
- /changelog page renders release notes; CHANGELOG.md mirrors it.
- 0.1.0 captures the storage/SQLite/settings/suggestions/backup work.

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

version.py

@@ -0,0 +1,26 @@
+"""App version + changelog.
+
+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.
+"""
+__version__ = "0.1.0"
+
+# 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.",
+        ],
+    },
+]