feat: replace wk1/wk4 targets with 6→8→10→12 rep ladder progression

Simplifies the progression model to a universal rep ladder: every exercise
follows 6→8→10→12 reps at current weight, then +5 lbs and reset to 6.
Replaces per-user wk1/wk4 rep and weight targets with a single
starting_weight field.

- Add Alembic migration to drop wk1_reps/wk4_reps/wk1_weight/wk4_weight,
  add starting_weight (migrated from wk1_weight)
- Run Alembic migrations on app startup instead of create_all, with
  auto-detection and stamping for legacy databases
- Include alembic/ and alembic.ini in Docker image
- Rewrite progression_service.get_suggestion() with ladder logic:
  climb, hold, weight_increase, hold_at_top, deload
- Replace wk1/wk4 grid in exercise cards with rep ladder progress bar
- Add color-coded progression badges by type
- Change weight log input from text to number with pre-filled suggestion
- Normalize weight input in routes (0→BW, bare number→N lbs)
- Remove schedule page (route, template, nav link, tests)
- Simplify user_programs.yaml from 4 fields to 1 per exercise
- Update all tests for new schema and progression logic

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/routes/logging.py

@@ -22,6 +22,23 @@ logger = structlog.get_logger(__name__)
 router = APIRouter(prefix="/log", tags=["logging"])
 
 
+def _normalize_weight(raw: str) -> str:
+    """Convert numeric weight input to display format.
+
+    '0' or '' → 'BW', bare number → '{n} lbs', already formatted → pass through.
+    """
+    raw = raw.strip()
+    if not raw or raw == "0":
+        return "BW"
+    try:
+        num = float(raw)
+        if num == int(num):
+            return f"{int(num)} lbs"
+        return f"{num} lbs"
+    except ValueError:
+        return raw
+
+
 @router.post("", response_class=HTMLResponse)
 async def log_set(
     request: Request,
@@ -38,7 +55,7 @@ async def log_set(
     workout_day_id = int(form.get("workout_day_id", 0))
     set_number = int(form.get("set_number", 1))
     reps = int(form.get("reps", 0))
-    weight = form.get("weight", "")
+    weight = _normalize_weight(form.get("weight", ""))
     felt_easy = form.get("felt_easy") == "on"
 
     # Get or create today's session
@@ -89,7 +106,7 @@ async def edit_log(
     log_service.update_log(
         log_id,
         reps_completed=int(form.get("reps", 0)),
-        weight_used=form.get("weight", ""),
+        weight_used=_normalize_weight(form.get("weight", "")),
         felt_easy=form.get("felt_easy") == "on",
         notes=form.get("notes"),
     )