feat: bundle Free-Exercise-DB + name matcher (step 1)

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>

tests/test_exercise_db.py

@@ -0,0 +1,55 @@
+"""Tests for the static exercise reference matcher."""
+import exercise_db
+
+
+class TestLookup:
+    def test_loads_bundled_data(self):
+        # Free-Exercise-DB ships ~870 entries; just sanity-check it's non-empty.
+        assert len(exercise_db.ALL) > 500
+
+    def test_exact_match(self):
+        m = exercise_db.lookup("Pullups")
+        assert m is not None
+        assert m["name"] == "Pullups"
+        assert "lats" in m["primary_muscles"]
+
+    def test_case_insensitive(self):
+        a = exercise_db.lookup("PULLUPS")
+        b = exercise_db.lookup("pullups")
+        assert a == b
+        assert a["name"] == "Pullups"
+
+    def test_hyphen_matches_compressed(self):
+        # User types "Pull-ups", DB has "Pullups". Compressed form catches it.
+        m = exercise_db.lookup("Pull-ups")
+        assert m is not None
+        assert m["name"] == "Pullups"
+
+    def test_multi_word_substring(self):
+        m = exercise_db.lookup("Romanian deadlift")
+        assert m is not None
+        assert m["name"] == "Romanian Deadlift"
+        assert "hamstrings" in m["primary_muscles"]
+
+    def test_ambiguous_single_token_returns_none(self):
+        # Lots of DB entries contain "Bench" / "Squat" / "Deadlift" as one
+        # token. Returning the shortest would mislead ("Bench" → "Bench Dips"
+        # → triceps). Refuse instead.
+        assert exercise_db.lookup("Bench") is None
+        assert exercise_db.lookup("Squat") is None
+        assert exercise_db.lookup("Deadlift") is None
+
+    def test_nonsense_returns_none(self):
+        assert exercise_db.lookup("flarbenstompf") is None
+        assert exercise_db.lookup("") is None
+        assert exercise_db.lookup("   ") is None
+
+    def test_returned_shape(self):
+        m = exercise_db.lookup("Pullups")
+        # The slim view drops `instructions` and `images`.
+        assert set(m.keys()) >= {
+            "name", "primary_muscles", "secondary_muscles",
+            "equipment", "category", "level",
+        }
+        assert "instructions" not in m
+        assert "images" not in m