feat: ZIP → rep lookup, member page redesign, letter improvements

ZIP lookup (GET /api/members/by-zip/{zip}):
- Two-step geocoding: Nominatim (ZIP → lat/lng) then Census TIGERweb
  Legislative identify (lat/lng → congressional district via GEOID)
- Handles at-large states (AK, DE, MT, ND, SD, VT, WY)
- Added rep_lookup health check to admin External API Health panel

congress_api.py fixes:
- parse_member_from_api: normalize state full name → 2-letter code
  (Congress.gov returns "Florida", DB expects "FL")
- parse_member_from_api: read district from top-level data field,
  not current_term (district is not inside the term object)

Celery beat: schedule sync_members daily at 1 AM UTC so chamber,
district, and contact info stay current without manual triggering

Members page redesign: photo avatars, party/state/chamber chips,
phone + website links, ZIP lookup form to find your reps

Draft letter improvements: pass rep_name from ZIP lookup so letter
opens with "Dear Representative Franklin," instead of generic salutation;
add has_document filter to bills list endpoint

UX additions: HelpTip component, How It Works page, "How it works"
sidebar nav link, collections page description copy

Authored-By: Jack Levy

backend/app/api/members.py

@@ -1,7 +1,23 @@
 import logging
+import re
 from datetime import datetime, timezone
 from typing import Optional
 
+_FIPS_TO_STATE = {
+    "01": "AL", "02": "AK", "04": "AZ", "05": "AR", "06": "CA",
+    "08": "CO", "09": "CT", "10": "DE", "11": "DC", "12": "FL",
+    "13": "GA", "15": "HI", "16": "ID", "17": "IL", "18": "IN",
+    "19": "IA", "20": "KS", "21": "KY", "22": "LA", "23": "ME",
+    "24": "MD", "25": "MA", "26": "MI", "27": "MN", "28": "MS",
+    "29": "MO", "30": "MT", "31": "NE", "32": "NV", "33": "NH",
+    "34": "NJ", "35": "NM", "36": "NY", "37": "NC", "38": "ND",
+    "39": "OH", "40": "OK", "41": "OR", "42": "PA", "44": "RI",
+    "45": "SC", "46": "SD", "47": "TN", "48": "TX", "49": "UT",
+    "50": "VT", "51": "VA", "53": "WA", "54": "WV", "55": "WI",
+    "56": "WY", "60": "AS", "66": "GU", "69": "MP", "72": "PR", "78": "VI",
+}
+
+import httpx
 from fastapi import APIRouter, Depends, HTTPException, Query
 from sqlalchemy import desc, func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -20,6 +36,139 @@ logger = logging.getLogger(__name__)
 router = APIRouter()
 
 
+@router.get("/by-zip/{zip_code}", response_model=list[MemberSchema])
+async def get_members_by_zip(zip_code: str, db: AsyncSession = Depends(get_db)):
+    """Return the House rep and senators for a ZIP code.
+    Step 1: Nominatim (OpenStreetMap) — ZIP → lat/lng.
+    Step 2: TIGERweb Legislative identify — lat/lng → congressional district.
+    """
+    if not re.fullmatch(r"\d{5}", zip_code):
+        raise HTTPException(status_code=400, detail="ZIP code must be 5 digits")
+
+    state_code: str | None = None
+    district_num: str | None = None
+
+    try:
+        async with httpx.AsyncClient(timeout=20.0) as client:
+            # Step 1: ZIP → lat/lng
+            r1 = await client.get(
+                "https://nominatim.openstreetmap.org/search",
+                params={"postalcode": zip_code, "country": "US", "format": "json", "limit": "1"},
+                headers={"User-Agent": "PocketVeto/1.0"},
+            )
+            places = r1.json() if r1.status_code == 200 else []
+            if not places:
+                logger.warning("Nominatim: no result for ZIP %s", zip_code)
+                return []
+
+            lat = places[0]["lat"]
+            lng = places[0]["lon"]
+
+            # Step 2: lat/lng → congressional district via TIGERweb identify (all layers)
+            half = 0.5
+            r2 = await client.get(
+                "https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/Legislative/MapServer/identify",
+                params={
+                    "f": "json",
+                    "geometry": f"{lng},{lat}",
+                    "geometryType": "esriGeometryPoint",
+                    "sr": "4326",
+                    "layers": "all",
+                    "tolerance": "2",
+                    "mapExtent": f"{float(lng)-half},{float(lat)-half},{float(lng)+half},{float(lat)+half}",
+                    "imageDisplay": "100,100,96",
+                },
+            )
+            if r2.status_code != 200:
+                logger.warning("TIGERweb returned %s for ZIP %s", r2.status_code, zip_code)
+                return []
+
+            identify_results = r2.json().get("results", [])
+            logger.info(
+                "TIGERweb ZIP %s layers: %s",
+                zip_code, [r.get("layerName") for r in identify_results],
+            )
+
+            for item in identify_results:
+                if "Congressional" not in (item.get("layerName") or ""):
+                    continue
+                attrs = item.get("attributes", {})
+                # GEOID = 2-char state FIPS + 2-char district (e.g. "1218" = FL-18)
+                geoid = str(attrs.get("GEOID") or "").strip()
+                if len(geoid) == 4:
+                    state_fips = geoid[:2]
+                    district_fips = geoid[2:]
+                    state_code = _FIPS_TO_STATE.get(state_fips)
+                    district_num = str(int(district_fips)) if district_fips.strip("0") else None
+                    if state_code:
+                        break
+
+                # Fallback: explicit field names
+                cd_field = next((k for k in attrs if re.match(r"CD\d+FP$", k)), None)
+                state_field = next((k for k in attrs if "STATEFP" in k.upper()), None)
+                if cd_field and state_field:
+                    state_fips = str(attrs[state_field]).zfill(2)
+                    district_fips = str(attrs[cd_field])
+                    state_code = _FIPS_TO_STATE.get(state_fips)
+                    district_num = str(int(district_fips)) if district_fips.strip("0") else None
+                    if state_code:
+                        break
+
+            if not state_code:
+                logger.warning(
+                    "ZIP %s: no CD found. Layers: %s",
+                    zip_code, [r.get("layerName") for r in identify_results],
+                )
+
+    except Exception as exc:
+        logger.warning("ZIP lookup error for %s: %s", zip_code, exc)
+        return []
+
+    if not state_code:
+        return []
+
+    members: list[MemberSchema] = []
+    seen: set[str] = set()
+
+    if district_num:
+        result = await db.execute(
+            select(Member).where(
+                Member.state == state_code,
+                Member.district == district_num,
+                Member.chamber == "House of Representatives",
+            )
+        )
+        member = result.scalar_one_or_none()
+        if member:
+            seen.add(member.bioguide_id)
+            members.append(MemberSchema.model_validate(member))
+    else:
+        # At-large states (AK, DE, MT, ND, SD, VT, WY)
+        result = await db.execute(
+            select(Member).where(
+                Member.state == state_code,
+                Member.chamber == "House of Representatives",
+            ).limit(1)
+        )
+        member = result.scalar_one_or_none()
+        if member:
+            seen.add(member.bioguide_id)
+            members.append(MemberSchema.model_validate(member))
+
+    result = await db.execute(
+        select(Member).where(
+            Member.state == state_code,
+            Member.chamber == "Senate",
+        )
+    )
+    for member in result.scalars().all():
+        if member.bioguide_id not in seen:
+            seen.add(member.bioguide_id)
+            members.append(MemberSchema.model_validate(member))
+
+    return members
+
+
 @router.get("", response_model=PaginatedResponse[MemberSchema])
 async def list_members(
     chamber: Optional[str] = Query(None),