Adds the static exercise reference data (~870 entries, public
domain, source: github.com/yuhonas/free-exercise-db) plus a
conservative name matcher. New endpoint:
GET /api/exercises/lookup?name=<name>
→ {"match": {"name", "primary_muscles", "secondary_muscles",
"equipment", "category", "level", ...}}
→ {"match": null} when nothing plausibly matches.
Matcher tiers (priority order):
1. exact (case-insensitive)
2. compressed exact ("Pull-ups" → "Pullups")
3. compressed substring, with a guard: single-token generics
like "Bench"/"Squat" return null instead of misleading the
user — the planned alias table will handle these properly.
4. token-overlap with ≥50% coverage of the user's tokens.
UI integration ("Trains: chest · shoulders") comes in step 2.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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