feat: add CSV export of workout history to dashboard

Add date range picker and download button to the dashboard page,
backed by GET /dashboard/export endpoint that returns a StreamingResponse
CSV file. Completes Phase 4 (final V2 improvement).

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

app/routes/dashboard.py

@@ -1,19 +1,26 @@
 """Progress dashboard routes.
 
-Displays summary statistics, volume charts, and per-exercise progress.
+Displays summary statistics, volume charts, per-exercise progress,
+and CSV export of workout history.
 """
 
+import csv
+import io
 import json
+import re
+from datetime import date, timedelta
+from typing import Optional
 
 import structlog
-from fastapi import APIRouter, Depends, Request
-from fastapi.responses import HTMLResponse
+from fastapi import APIRouter, Depends, Query, Request
+from fastapi.responses import HTMLResponse, StreamingResponse
 from sqlmodel import Session
 
 from app.database import get_db_session
 from app.models.user import User
 from app.services.analytics_service import AnalyticsService
 from app.services.exercise_service import ExerciseService
+from app.services.export_service import ExportService
 from app.services.progression_service import ProgressionService
 from app.utils.auth import require_active_profile
 
@@ -36,6 +43,10 @@ async def dashboard(
     exercise_service = ExerciseService(session)
     exercises = exercise_service.list_exercises()
 
+    today = date.today()
+    export_start = (today - timedelta(days=30)).isoformat()
+    export_end = today.isoformat()
+
     templates = request.app.state.templates
     return templates.TemplateResponse("pages/dashboard.html", {
         "request": request,
@@ -43,9 +54,52 @@ async def dashboard(
         "volume_data_json": json.dumps(volume_data),
         "exercises": exercises,
         "active_profile": profile,
+        "export_start_date": export_start,
+        "export_end_date": export_end,
     })
 
 
+@router.get("/export")
+async def export_csv(
+    request: Request,
+    start_date: Optional[str] = Query(None),
+    end_date: Optional[str] = Query(None),
+    session: Session = Depends(get_db_session),
+    profile: User = Depends(require_active_profile),
+):
+    """Export workout history as a CSV file download."""
+    today = date.today()
+    default_start = today - timedelta(days=30)
+
+    try:
+        parsed_start = date.fromisoformat(start_date) if start_date else default_start
+    except ValueError:
+        parsed_start = default_start
+
+    try:
+        parsed_end = date.fromisoformat(end_date) if end_date else today
+    except ValueError:
+        parsed_end = today
+
+    export_service = ExportService(session)
+    rows = export_service.get_export_rows(profile.id, parsed_start, parsed_end)
+
+    output = io.StringIO()
+    headers = ["date", "workout_type", "exercise", "set_number", "reps", "weight", "felt_easy"]
+    writer = csv.DictWriter(output, fieldnames=headers)
+    writer.writeheader()
+    writer.writerows(rows)
+
+    safe_name = re.sub(r"[^a-z0-9_]", "", profile.display_name.lower().replace(" ", "_"))
+    filename = f"sneakyswole_{safe_name}_{parsed_start.isoformat()}_to_{parsed_end.isoformat()}.csv"
+
+    return StreamingResponse(
+        iter([output.getvalue()]),
+        media_type="text/csv",
+        headers={"Content-Disposition": f'attachment; filename="{filename}"'},
+    )
+
+
 @router.get("/exercise/{exercise_id}", response_class=HTMLResponse)
 async def exercise_progress(
     exercise_id: int,

app/services/export_service.py

@@ -0,0 +1,80 @@
+"""Export service for generating CSV-ready workout history data.
+
+Queries workout logs joined with sessions, days, and exercises
+to produce flat rows suitable for CSV export.
+"""
+
+from datetime import date
+
+import structlog
+from sqlmodel import Session, select
+
+from app.models.exercise import Exercise
+from app.models.workout_log import WorkoutLog
+from app.models.workout_session import WorkoutSession
+
+logger = structlog.get_logger(__name__)
+
+
+class ExportService:
+    """Builds export-ready workout history rows.
+
+    Args:
+        session: An active SQLModel Session.
+    """
+
+    def __init__(self, session: Session) -> None:
+        self._session = session
+
+    def get_export_rows(
+        self, user_id: int, start_date: date, end_date: date,
+    ) -> list[dict]:
+        """Get flat workout log rows for CSV export.
+
+        Args:
+            user_id: The user whose data to export.
+            start_date: Inclusive start of date range.
+            end_date: Inclusive end of date range.
+
+        Returns:
+            List of dicts with keys: date, workout_type, exercise,
+            set_number, reps, weight, felt_easy.
+        """
+        sessions = self._session.exec(
+            select(WorkoutSession)
+            .where(
+                WorkoutSession.user_id == user_id,
+                WorkoutSession.date >= start_date,
+                WorkoutSession.date <= end_date,
+            )
+            .order_by(WorkoutSession.date.asc())
+        ).all()
+
+        if not sessions:
+            return []
+
+        # Pre-load exercises for name lookup
+        exercises = self._session.exec(select(Exercise)).all()
+        exercise_map = {e.id: e for e in exercises}
+
+        rows = []
+        for ws in sessions:
+            logs = self._session.exec(
+                select(WorkoutLog)
+                .where(WorkoutLog.session_id == ws.id)
+                .order_by(WorkoutLog.exercise_id, WorkoutLog.set_number)
+            ).all()
+
+            for log_entry in logs:
+                exercise = exercise_map.get(log_entry.exercise_id)
+                rows.append({
+                    "date": ws.date.isoformat(),
+                    "workout_type": exercise.workout_day if exercise else "Unknown",
+                    "exercise": exercise.name if exercise else "Unknown",
+                    "set_number": log_entry.set_number,
+                    "reps": log_entry.reps_completed,
+                    "weight": log_entry.weight_used,
+                    "felt_easy": "Yes" if log_entry.felt_easy else "No",
+                })
+
+        return rows

app/templates/pages/dashboard.html

@@ -42,5 +42,8 @@
         {% endfor %}
     </ul>
 </article>
+
+<!-- Export -->
+{% include "partials/export_form.html" %}
 {% endif %}
 {% endblock %}

app/templates/partials/export_form.html

@@ -0,0 +1,19 @@
+<article>
+    <header><h3>Export Workout History</h3></header>
+    <form method="get" action="/dashboard/export">
+        <div class="grid">
+            <label>
+                Start Date
+                <input type="date" name="start_date" value="{{ export_start_date }}">
+            </label>
+            <label>
+                End Date
+                <input type="date" name="end_date" value="{{ export_end_date }}">
+            </label>
+            <label>
+                &nbsp;
+                <button type="submit">Download CSV</button>
+            </label>
+        </div>
+    </form>
+</article>