feat(sfm): strip "- Loc N" suffix from operator-typed project names

Operators sometimes bake location identifiers into the project string
for email-readability — "Fay - Locks & Dam No3 - Loc 2 - 735 Bunola"
where "Fay - Locks & Dam No3" is the actual project and "- Loc 2 -
735 Bunola" is location info that already lives in sensor_location.
Without stripping, every "- Loc N" variant became a separate project,
fragmenting what should be one project with several locations.

Backend:
- New _extract_project_root() helper.  Regex matches " - Loc N" / "-Loc3" /
  " - Location #5" / etc. with case-insensitive multi-dash support; strips
  from that marker forward and cleans up dangling separators.  Strings
  without a Loc-marker pass through unchanged.

- Cluster dataclass adds project_root field alongside project_raw.
  project_raw stays the operator-typed string for display ("hover to see
  what was actually typed").  project_root is what gets normalised for
  matching and used as the suggested project name.

- _ensure_project + _ensure_location now do normalisation-aware dedup
  before creating: a cluster of "SR81" and a cluster of "SR 81" (which
  normalise to the same string) collapse into one project on apply,
  even when applied in the same bulk operation.  Avoids UNIQUE
  constraint collisions and duplicate-named-by-spacing projects.

Frontend:
- Wizard cluster cards show "↳ stripped trailing 'Loc N' suffix; operator
  typed: <raw>" when project_root differs from project_raw, so the
  operator can see at a glance what the parser did to the string.

Real-data results: against the same 10,055 SFM events, confidence
distribution improved from 37/14/8 (high/med/low) to 43/9/7.  "Fay -
Locks & Dam No3" now appears as ONE project across 6 cluster instances
spanning 3 serials and 6 different locations — exactly the
"one project, many locations" model the user described.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

templates/admin/metadata_backfill.html

@@ -288,6 +288,9 @@ function _renderCluster(s) {
                 </div>
                 <div class="text-sm text-gray-700 dark:text-gray-300 mt-2 space-y-1">
                     <div><span class="text-gray-500 dark:text-gray-400 w-24 inline-block">Project:</span> ${_matchPill(s.project_match, s.project_match_score, s.project_suggested_name, s.project_existing_name)}</div>
+                    ${(s.project_root && s.project_raw && s.project_root !== s.project_raw)
+                        ? `<div class="text-xs text-gray-500 dark:text-gray-400 pl-24">↳ stripped trailing "Loc N" suffix; operator typed: <em>"${_esc(s.project_raw)}"</em></div>`
+                        : ''}
                     <div><span class="text-gray-500 dark:text-gray-400 w-24 inline-block">Location:</span> ${_matchPill(s.location_match, s.location_match_score, s.location_suggested_name, s.location_existing_name)}</div>
                     <div><span class="text-gray-500 dark:text-gray-400 w-24 inline-block">Assignment:</span> ${_fmtDateTime(s.proposed_assigned_at)} → ${s.proposed_assigned_until ? _fmtDateTime(s.proposed_assigned_until) : '<span class="text-green-700 dark:text-green-400 font-medium">present (active)</span>'}</div>
                     ${s.client_raw ? `<div><span class="text-gray-500 dark:text-gray-400 w-24 inline-block">Client:</span> <em>${_esc(s.client_raw)}</em></div>` : ''}