perf: Optimize snapshot database queries (fix N+1 issue)

[matthewro7263-hub]

💡 What: Replaced the flatMap pattern for fetching storyboard panels with a single inArray query.
🎯 Why: The previous approach executed a separate database query for every single storyboard returned from the project (an N+1 query problem). Fetching all panel rows in a single batch using the IN clause dramatically reduces round-trips and SQLite overhead.
📊 Measured Improvement:
In a benchmark with 100 storyboards (10 panels each, totaling 1000 panels fetched):

• N+1 (Baseline): ~10.0 - 13.0 ms
• Optimized inArray: ~4.3 - 4.5 ms
• Improvement: ~65% reduction in query execution time for this operation.

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PR created automatically by Jules for task 9755194764164504910 started by @matthewro7263-hub

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[matthewro7263-hub]

Review notes before merge:

1. Rebase onto current main to clear the merge conflict.
2. PR description references SQLite + better-sqlite3 overhead, but the repo has since migrated to Postgres (Drizzle). Please re-verify the inArray query plan under Postgres and re-run the 1000-panel benchmark on the new backend — IN (...) semantics differ slightly and very large arrays may need chunking.
3. Add/refresh a unit test that exercises the batched fetch path with >100 panels to lock in the perf improvement.
4. Confirm no callers still depend on the old flatMap shape.

Aligned with keep-it-free goal: ✅ pure perf win, reduces server cost.

[matthewro7263-hub]

Going to close this one out — it's got merge conflicts against current main, and the same N+1 area was already addressed by the more recent #62 (snapshot panel loading) and the still-open #65 (project archive export). Rather than rebasing 3-week-old changes, suggest closing this and letting the newer PRs cover it. Nice benchmarks though.

[matthewro7263-hub]

Closing as duplicate — the same N+1 fix landed in #71.