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>

alembic/versions/b2c3d4e5f6g7_simplify_to_starting_weight.py

@@ -0,0 +1,45 @@
+"""simplify user_exercise_programs to starting_weight
+
+Revision ID: b2c3d4e5f6g7
+Revises: a1b2c3d4e5f6
+Create Date: 2026-03-13
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+import sqlmodel
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'b2c3d4e5f6g7'
+down_revision: Union[str, Sequence[str], None] = 'a1b2c3d4e5f6'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    with op.batch_alter_table('user_exercise_programs') as batch_op:
+        batch_op.add_column(sa.Column('starting_weight', sa.String(), nullable=False, server_default=''))
+
+    op.execute("UPDATE user_exercise_programs SET starting_weight = wk1_weight")
+
+    with op.batch_alter_table('user_exercise_programs') as batch_op:
+        batch_op.drop_column('wk1_reps')
+        batch_op.drop_column('wk4_reps')
+        batch_op.drop_column('wk1_weight')
+        batch_op.drop_column('wk4_weight')
+
+
+def downgrade() -> None:
+    with op.batch_alter_table('user_exercise_programs') as batch_op:
+        batch_op.add_column(sa.Column('wk1_reps', sa.String(), server_default=''))
+        batch_op.add_column(sa.Column('wk4_reps', sa.String(), server_default=''))
+        batch_op.add_column(sa.Column('wk1_weight', sa.String(), server_default=''))
+        batch_op.add_column(sa.Column('wk4_weight', sa.String(), server_default=''))
+
+    op.execute("UPDATE user_exercise_programs SET wk1_weight = starting_weight")
+
+    with op.batch_alter_table('user_exercise_programs') as batch_op:
+        batch_op.drop_column('starting_weight')