Add MVP frontend scaffold with FastAPI + HTMX + TailwindCSS

- Created complete frontend structure with Jinja2 templates
- Implemented three main pages: Dashboard, Fleet Roster, and Unit Detail
- Added HTMX auto-refresh for real-time updates (10s interval)
- Integrated dark/light mode toggle with localStorage persistence
- Built responsive card-based UI with sidebar navigation
- Created API endpoints for status snapshot, roster, unit details, and photos
- Added mock data service for development (emit_status_snapshot)
- Implemented tabbed interface on unit detail page (Photos, Map, History)
- Integrated Leaflet maps for unit location visualization
- Configured static file serving and photo management
- Updated requirements.txt with Jinja2 and aiofiles
- Reorganized backend structure into routers and services
- Added comprehensive FRONTEND_README.md documentation

Frontend features:
- Auto-refreshing dashboard with fleet summary and alerts
- Sortable fleet roster table (prioritizes Missing > Pending > OK)
- Unit detail view with status, deployment info, and notes
- Photo gallery with thumbnail navigation
- Interactive maps showing unit coordinates
- Consistent styling with brand colors (orange, navy, burgundy)

Ready for integration with real Series3 emitter data.

backend/main.py

@@ -0,0 +1,108 @@
+from fastapi import FastAPI, Request
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.staticfiles import StaticFiles
+from fastapi.templating import Jinja2Templates
+from fastapi.responses import HTMLResponse
+
+from backend.database import engine, Base
+from backend.routers import roster, units, photos
+from backend.services.snapshot import emit_status_snapshot
+
+# Create database tables
+Base.metadata.create_all(bind=engine)
+
+# Initialize FastAPI app
+app = FastAPI(
+    title="Seismo Fleet Manager",
+    description="Backend API for managing seismograph fleet status",
+    version="0.1.0"
+)
+
+# Configure CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Mount static files
+app.mount("/static", StaticFiles(directory="backend/static"), name="static")
+
+# Setup Jinja2 templates
+templates = Jinja2Templates(directory="templates")
+
+# Include API routers
+app.include_router(roster.router)
+app.include_router(units.router)
+app.include_router(photos.router)
+
+
+# Legacy routes from the original backend
+from backend import routes as legacy_routes
+app.include_router(legacy_routes.router)
+
+
+# HTML page routes
+@app.get("/", response_class=HTMLResponse)
+async def dashboard(request: Request):
+    """Dashboard home page"""
+    return templates.TemplateResponse("dashboard.html", {"request": request})
+
+
+@app.get("/roster", response_class=HTMLResponse)
+async def roster_page(request: Request):
+    """Fleet roster page"""
+    return templates.TemplateResponse("roster.html", {"request": request})
+
+
+@app.get("/unit/{unit_id}", response_class=HTMLResponse)
+async def unit_detail_page(request: Request, unit_id: str):
+    """Unit detail page"""
+    return templates.TemplateResponse("unit_detail.html", {
+        "request": request,
+        "unit_id": unit_id
+    })
+
+
+@app.get("/partials/roster-table", response_class=HTMLResponse)
+async def roster_table_partial(request: Request):
+    """Partial template for roster table (HTMX)"""
+    from datetime import datetime
+    snapshot = emit_status_snapshot()
+
+    units_list = []
+    for unit_id, unit_data in snapshot["units"].items():
+        units_list.append({
+            "id": unit_id,
+            "status": unit_data["status"],
+            "age": unit_data["age"],
+            "last_seen": unit_data["last"],
+            "deployed": unit_data["deployed"],
+            "note": unit_data.get("note", ""),
+        })
+
+    # Sort by status priority (Missing > Pending > OK) then by ID
+    status_priority = {"Missing": 0, "Pending": 1, "OK": 2}
+    units_list.sort(key=lambda x: (status_priority.get(x["status"], 3), x["id"]))
+
+    return templates.TemplateResponse("partials/roster_table.html", {
+        "request": request,
+        "units": units_list,
+        "timestamp": datetime.now().strftime("%H:%M:%S")
+    })
+
+
+@app.get("/health")
+def health_check():
+    """Health check endpoint"""
+    return {
+        "message": "Seismo Fleet Manager v0.1",
+        "status": "running"
+    }
+
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run(app, host="0.0.0.0", port=8001)