Keep Token activity inside the selected range

[thrr87]

Closes #43.

Fix

• chart only daily account buckets fully contained in the selected range
• show a clear empty state when the current window has no complete day
• prepare v0.2.5

Evidence

• regression test failed with boundary buckets [100, 200, 300, 400] instead of [200, 300], then passed after the fix
• 504 Swift tests pass
• full-screen QA passed for Current window and 4 weeks
• production bundle 0.2.5 build 6 passes codesign verification