fix: include source in exercise_snapshot for v2 by-date endpoint

[johnpena]

Summary

• The v2 _buildExerciseEntryWithSnapshot function omits source from the exercise_snapshot object
• The frontend checks exercise_snapshot.source to decide whether to prepend /uploads/exercises/ to image paths
• Without source in the snapshot, it's undefined (falsy), so the frontend uses raw image filenames as URLs, resulting in 404s for all exercise images in the diary view

Test plan

• Navigate to the diary page with exercise entries that have images from FreeExerciseDB
• Verify exercise images load correctly (no broken image icons)
• Verify the image URLs include the /uploads/exercises/ prefix

[gemini-code-assist]

Code Review

This pull request updates the exercise entry history service to include the source field in the exercise snapshot. The review feedback suggests also including source_id and calories_per_hour to maintain parity with the legacy API and ensure compliance with the defined response schema.

[gemini-code-assist]

While adding source fixes the reported image loading issue, the exercise_snapshot is still missing source_id and calories_per_hour. These fields were present in the legacy implementation and are defined in the exerciseSnapshotResponseSchema. Including them ensures full parity with the legacy API and prevents potential regressions in the frontend.

Suggested change

	id: entryData.exercise_id as string,
	name: exercise_name as string,
	category: (category as string) ?? null,
	source: (source as string) ?? null,
	images: _parseJsonArray(images),
	id: entryData.exercise_id as string,
	name: exercise_name as string,
	category: (category as string) ?? null,
	source: (source as string) ?? null,
	source_id: (entryData.source_id as string) ?? null,
	calories_per_hour: (entryData.calories_per_hour as number) ?? null,
	images: _parseJsonArray(images),

[apedley]

5 lines above, source_id is already sent so I don't know if sending the data twice is the right fix. I don't see where the frontend would expect it in the snapshot object. I only see it referenced like:

exerciseEntry.source
	? `/uploads/exercises/${snapshot.images[0]}`
	: snapshot.images[0]

Are you seeing image 404s? Where?