Allow decimal weights and remove last-session set chip (#119)

### Motivation
- Allow users to enter free-form decimal weights in the session logger and remove the small per-exercise "last session" label showing previous weight/reps to simplify the UI and avoid redundancy.

### Description
- Change the weight input `step` from `0.5` to `any` so decimal values of any precision are accepted (`weightInput.step = 'any'`).
- Remove the `renderPreviousChip` function and the code that appended the per-exercise `Last: … kg · … reps` chip from `renderExercise` to drop the small last-session label.
- Keep existing behaviour that still reads previous-set values for pre-filling inputs when available.

------
[Codex Task](https://chatgpt.com/codex/tasks/task_e_69bd13651728832580bee57c0d9205d3)

Author: rodrigogiraoserrao

workout-session-logger.html

@@ -371,17 +371,6 @@ <h2 style="margin: 0;">Workout tools</h2>
                 return state.latestSession.exercise_blocks.find((ex) => ex.exercise_name === exerciseName) || null;
             }
 
-            function renderPreviousChip(block) {
-                const prev = findPreviousExercise(block.exercise_name);
-                if (!prev) return null;
-                const firstCompleted = prev.sets.find((set) => Number.isFinite(set.weight) || Number.isFinite(set.reps));
-                if (!firstCompleted) return null;
-                const chip = document.createElement('span');
-                chip.className = 'chip';
-                chip.textContent = `Last: ${firstCompleted.weight ?? '—'} kg · ${firstCompleted.reps ?? '—'} reps`;
-                return chip;
-            }
-
             function createRepsInput(exerciseName, setIndex, initialValue, placeholder = 'Reps') {
                 const input = document.createElement('input');
                 input.type = 'number';
@@ -421,7 +410,7 @@ <h2 style="margin: 0;">Workout tools</h2>
                 const weightInput = document.createElement('input');
                 weightInput.type = 'number';
                 weightInput.inputMode = 'decimal';
-                weightInput.step = '0.5';
+                weightInput.step = 'any';
                 weightInput.placeholder = 'Weight';
                 weightInput.dataset.exerciseName = exerciseName;
                 weightInput.dataset.setIndex = setIndex;
@@ -477,8 +466,6 @@ <h2 style="margin: 0;">Workout tools</h2>
                     ? 'AMRAP'
                     : `${block.min_reps ?? 0}–${block.max_reps ?? 0} reps`;
 
-                const previousChip = renderPreviousChip(block);
-
                 const body = document.createElement('div');
                 body.className = 'exercise-body';
 
@@ -496,10 +483,6 @@ <h2 style="margin: 0;">Workout tools</h2>
                 infoRow.appendChild(notesMeta);
                 infoRow.appendChild(repRangeMeta);
 
-                if (previousChip) {
-                    infoRow.appendChild(previousChip);
-                }
-
                 const setsGrid = document.createElement('div');
                 setsGrid.className = 'stack';