Add time-based filtering to Popular Links

[dfcarney]

Summary

• Adds 7-day, 30-day, and all-time filter buttons to the Popular Links section on the home page
• Adds LoadStatsSince DB method backed by a single Stats/Links join query and an index on Stats(Created) for efficient time-filtered aggregation
• Parses period as a bounded duration so pre-populated filters and arbitrary positive periods up to 365 days are supported without allowing unbounded full-history DB scans
• Time-filtered queries read directly from the DB without calling flushStats, avoiding serialization of home page requests under load (stats are at most ~1 minute stale via the periodic flush loop)
• Closes DB result sets in the new query path and adjacent DB readers

Test plan

• New unit test for LoadStatsSince in db_test.go, including stale stats for missing links
• New integration test TestServeHomePeriodFilter in golink_test.go covering all-time, 7d, 30d, arbitrary duration, and invalid period fallback
• New unit test coverage for parseStatsPeriod, including bounds and overflow cases
• go test ./...
• go test -race ./...
• Local UI screenshots captured for all-time and 7-day filter states

[Copilot]

Pull request overview

Adds time-based filtering (7-day, 30-day, all-time) to the “Popular Links” section on the home page, backed by a new DB query path and an index to support efficient time-windowed aggregation.

Changes:

• Adds period filter links to the home page template and plumbs the selected period through homeData.
• Implements SQLiteDB.LoadStatsSince(since) and wires serveHome to use it for 7d/30d filters.
• Updates DB schema with an index on Stats(Created) and adds unit/integration tests for the new filtering behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tmpl/home.html	Adds UI filter links and active-state styling based on .Period.
golink.go	Reads ?period= and uses DB-backed stats for 7d/30d; passes .Period to the template.
db.go	Introduces LoadStatsSince to aggregate clicks since a given timestamp.
schema.sql	Adds an index on Stats.Created for time-based filtering queries.
db_test.go	Adds unit test coverage for LoadStatsSince.
golink_test.go	Adds integration test coverage for home page period filtering.

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[mikeodr]

My concerns largely align with the copilot check.

There's some cleanup missing in the queries, and doing a full load could be a bit more optimized.

Any screenshots of what the UIs look like would be helpful as well.

[dfcarney]

Updated this branch and addressed the outstanding review feedback.

Changes since the prior review:

• Rebased onto the latest main so the branch is no longer out of date.
• Reworked LoadStatsSince to use a single Stats/Links join, which removes the per-request LoadAll and naturally excludes stats for deleted/missing links.
• Added defer rows.Close() in the new query path and adjacent DB readers.
• Changed period parsing to support arbitrary positive durations with a 365-day cap.
• Fixed ignored errors in the new home-period integration test.
• Added tests for missing-link stats, arbitrary duration periods, invalid fallback, bounds, and overflow cases.

Local verification:

• go test ./...
• go test -race ./...
• UI spot check for all-time and 7-day filter states using a seeded dev DB.