feat: monitoring session improvements — UTC fix, period hours, calendar, session detail

- Fix UTC display bug: upload_nrl_data now wraps RNH datetimes with
  local_to_utc() before storing, matching patch_session behavior.
  Period type and label are derived from local time before conversion.

- Add period_start_hour / period_end_hour to MonitoringSession model
  (nullable integers 0–23). Migration: migrate_add_session_period_hours.py

- Update patch_session to accept and store period_start_hour / period_end_hour.
  Response now includes both fields.

- Update get_project_sessions to compute "Effective: M/D H:MM AM → M/D H:MM AM"
  string from period hours and pass it to session_list.html.

- Rework period edit UI in session_list.html: clicking the period badge now
  opens an inline editor with period type selector + start/end hour inputs.
  Selecting a period type pre-fills default hours (Day: 7–19, Night: 19–7).

- Wire period hours into _build_location_data_from_sessions: uses
  period_start/end_hour when set, falls back to hardcoded defaults.

- RND viewer: inject SESSION_PERIOD_START/END_HOUR from template context.
  renderTable() dims rows outside the period window (opacity-40) with a
  tooltip; shows "(N in period window)" in the row count.

- New session detail page at /api/projects/{id}/sessions/{id}/detail:
  shows breadcrumb, files list with View/Download/Report actions,
  editable session info form (label, period type, hours, times).

- Add local_datetime_input Jinja filter for datetime-local input values.

- Monthly calendar view: new get_sessions_calendar endpoint returns
  sessions_calendar.html partial; added below sessions list in detail.html.
  Color-coded per NRL with legend, HTMX prev/next navigation, session dots
  link to detail page.

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

backend/models.py

@@ -303,6 +303,12 @@ class MonitoringSession(Base):
     # weekday_day | weekday_night | weekend_day | weekend_night
     period_type = Column(String, nullable=True)
 
+    # Effective monitoring window (hours 0–23).  Night sessions cross midnight
+    # (period_end_hour < period_start_hour).  NULL = no filtering applied.
+    # e.g.  Day: start=7, end=19   Night: start=19, end=7
+    period_start_hour = Column(Integer, nullable=True)
+    period_end_hour   = Column(Integer, nullable=True)
+
     # Snapshot of device configuration at recording time
     session_metadata = Column(Text, nullable=True)  # JSON