Add per-company backup reports (printable page and CSV)

/report.html shows one company's backups over the last 7, 30 or 90
days, chosen in the page and kept in the URL so reports can be
bookmarked or linked. Reached from Reports in the top bar, or a
company's name in a job's detail.

- Summary (jobs, runs, success rate, warnings, failures, overdue now);
  per job: run counts, success rate (successful / finished runs), last
  result and last successful backup; a day-by-day strip; every warning
  and failure with its message
- Print / Save as PDF: a print stylesheet prints light whatever the
  screen theme, hides the controls, keeps rows and strips whole across
  pages, and keeps the coloured cells and badges
- Days before a job was first known show as "Not monitored yet"
  rather than as missed backups, so a 90-day report for a newly added
  client doesn't look like 60 days of failures
- CSV of every run (full messages, times in the browser's time zone,
  UTF-8 BOM for Excel, formula-like values defused with a leading ')

Backend: GET /api/v1/tenants, /api/v1/reports/tenant and
/api/v1/reports/tenant.csv; periods capped at retention. tzdata added
for systems without time zone data. Frontend status and day-strip
helpers moved out of app.js into status.js / history.js for reuse.

Tested: 9 new backend tests; in the browser against the API with 30
days of demo history (summary, issues, strips, 7/30/90 switching,
CSV download with BOM, print styles applied on screen), mock mode and
phone width.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

backend/app/repo.py

@@ -42,6 +42,13 @@ def list_jobs(conn: sqlite3.Connection) -> list[dict[str, Any]]:
     return [{k: row[k] for k in _SUMMARY_FIELDS} for row in rows]
 
 
+def list_tenant_jobs(conn: sqlite3.Connection, tenant_id: int) -> list[dict[str, Any]]:
+    """A company's jobs with their current status, for reports."""
+    rows = conn.execute(_JOB_SQL + " WHERE j.tenant_id = ? ORDER BY j.name", (tenant_id,)).fetchall()
+    fields = (*_SUMMARY_FIELDS, "last_status")
+    return [{k: row[k] for k in fields} for row in rows]
+
+
 def get_job(conn: sqlite3.Connection, job_id: int) -> dict[str, Any] | None:
     row = conn.execute(_JOB_SQL + " WHERE j.id = ?", (job_id,)).fetchone()
     if row is None: