refactor(nav): rename Fleet→Devices, add Tools entry, move workflows to Tools

Sidebar evolved from "Fleet defaults to seismograph dashboard" to
"Devices defaults to unified roster" + a new "Tools" entry housing the
active operator workflows.

Sidebar (6 items):
  Dashboard · Devices · Projects · Tools · Job Planner · Settings

Changes:
- templates/base.html: renamed Fleet → Devices.  Default route changed
  from /seismographs to /roster — clicking Devices now lands on the
  unified all-devices view, then operators drill into type-specific
  layouts via the tab strip.  Tools entry added between Projects and
  Job Planner; highlights when on /tools or any of its linked workflow
  pages.
- templates/partials/fleet_tab_strip.html: reordered tabs so "All
  Devices" comes first (matches the new default landing).
  Seismographs → SLMs → Modems follow.
- templates/tools.html (new) + /tools route in main.py: card grid hub
  for active workflows.
    • Pair Devices — links to /pair-devices
    • Project Tidy — links to /settings/developer/project-tidy
    • Backfill from event metadata — /settings/developer/metadata-backfill
    • Reports — info card pointing to project detail pages where
      Excel report generation actually lives (per-project context)
    • Swap Detection — greyed-out placeholder for Phase 5c
- templates/settings.html: removed Project Tidy + Metadata Backfill
  cards from Settings → Developer.  They now live in Tools.  Settings
  → Developer retains the truly admin/dev surfaces (Watcher Manager,
  SFM Admin).

The workflow page URLs (/settings/developer/project-tidy,
/settings/developer/metadata-backfill) stay where they are — only the
nav entry point changes.  Bookmarks still work.

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

backend/main.py

@@ -258,6 +258,14 @@ async def project_tidy_page(request: Request):
     return templates.TemplateResponse("admin/project_tidy.html", {"request": request})
 
 
+@app.get("/tools", response_class=HTMLResponse)
+async def tools_page(request: Request):
+    """Tools / workflow hub.  Active operator workflows (device pairing,
+    project tidy, metadata backfill, future swap detection, report
+    generators) all live here in card form."""
+    return templates.TemplateResponse("tools.html", {"request": request})
+
+
 @app.get("/modems", response_class=HTMLResponse)
 async def modems_page(request: Request):
     """Field modems management dashboard"""