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/routes.py

@@ -0,0 +1,82 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+from pydantic import BaseModel
+from datetime import datetime
+from typing import Optional, List
+
+from backend.database import get_db
+from backend.models import Emitter
+
+router = APIRouter()
+
+
+# Pydantic schemas for request/response validation
+class EmitterReport(BaseModel):
+    unit: str
+    unit_type: str
+    timestamp: str
+    file: str
+    status: str
+
+
+class EmitterResponse(BaseModel):
+    id: str
+    unit_type: str
+    last_seen: datetime
+    last_file: str
+    status: str
+    notes: Optional[str] = None
+
+    class Config:
+        from_attributes = True
+
+
+@router.post("/emitters/report", status_code=200)
+def report_emitter(report: EmitterReport, db: Session = Depends(get_db)):
+    """
+    Endpoint for emitters to report their status.
+    Creates a new emitter if it doesn't exist, or updates an existing one.
+    """
+    try:
+        # Parse the timestamp
+        timestamp = datetime.fromisoformat(report.timestamp.replace('Z', '+00:00'))
+    except ValueError:
+        raise HTTPException(status_code=400, detail="Invalid timestamp format")
+
+    # Check if emitter already exists
+    emitter = db.query(Emitter).filter(Emitter.id == report.unit).first()
+
+    if emitter:
+        # Update existing emitter
+        emitter.unit_type = report.unit_type
+        emitter.last_seen = timestamp
+        emitter.last_file = report.file
+        emitter.status = report.status
+    else:
+        # Create new emitter
+        emitter = Emitter(
+            id=report.unit,
+            unit_type=report.unit_type,
+            last_seen=timestamp,
+            last_file=report.file,
+            status=report.status
+        )
+        db.add(emitter)
+
+    db.commit()
+    db.refresh(emitter)
+
+    return {
+        "message": "Emitter report received",
+        "unit": emitter.id,
+        "status": emitter.status
+    }
+
+
+@router.get("/fleet/status", response_model=List[EmitterResponse])
+def get_fleet_status(db: Session = Depends(get_db)):
+    """
+    Returns a list of all emitters and their current status.
+    """
+    emitters = db.query(Emitter).all()
+    return emitters