docs: Add voting setup troubleshooting guide

Documents the issue where elections are missing ElGamal encryption parameters
which are required for the voting system to work. Provides 3 options to fix:
1. Database SQL update
2. Adminer UI
3. Fresh database reset

Explains root cause and how to verify the fix worked.

e-voting-system/VOTING_SETUP_ISSUE.md

@@ -0,0 +1,136 @@
+# Voting Setup Issue - Solution
+
+## Problem
+
+Users cannot vote because:
+1. Elections don't have ElGamal encryption keys (`elgamal_p`, `elgamal_g`)
+2. The voting interface fails when trying to get public keys
+
+## Root Cause
+
+The database initialization script `docker/create_active_election.sql` didn't set the ElGamal parameters, even though the init.sql had `elgamal_p = 23, elgamal_g = 5`.
+
+## Fix
+
+### Option 1: Fix via Database (Recommended)
+
+Connect to the database and update the elections with ElGamal parameters:
+
+```bash
+# Connect to MariaDB
+docker compose exec mariadb mariadb -u evoting_user -pevoting_pass123 evoting_db
+
+# Run this SQL:
+UPDATE elections SET elgamal_p = 23, elgamal_g = 5;
+
+# Verify:
+SELECT id, name, elgamal_p, elgamal_g FROM elections LIMIT 5;
+
+# Exit
+exit
+```
+
+### Option 2: Use Adminer UI
+
+1. Go to http://localhost:8081
+2. Login:
+   - Server: `mariadb`
+   - User: `evoting_user`
+   - Password: `evoting_pass123`
+   - Database: `evoting_db`
+3. Click on `elections` table
+4. Edit each row and set:
+   - `elgamal_p` = 23
+   - `elgamal_g` = 5
+
+### Option 3: Fresh Database Reset
+
+```bash
+# Stop and remove all data
+docker compose down -v
+
+# Start fresh
+docker compose -f docker-compose.multinode.yml up -d
+
+# Wait 40 seconds for initialization
+sleep 40
+
+# Verify elections have keys
+curl http://localhost:8000/api/elections/debug/all | jq '.elections[0] | {id, name, elgamal_p, elgamal_g}'
+```
+
+## Verify Fix Worked
+
+After fixing, test:
+
+```bash
+# Check election keys are set
+curl http://localhost:8000/api/elections/debug/all | jq '.elections[0] | {id, name, elgamal_p, elgamal_g}'
+
+# Should show:
+# {
+#   "id": 1,
+#   "name": "...",
+#   "elgamal_p": 23,
+#   "elgamal_g": 5
+# }
+
+# Get public keys (should work now)
+curl http://localhost:8000/api/votes/public-keys?election_id=1 | jq '.'
+```
+
+## Why This Happened
+
+The SQL scripts do this:
+1. `docker/init.sql` - Creates elections with `elgamal_p = 23, elgamal_g = 5`
+2. `docker/populate_past_elections.sql` - Inserts past elections (no ElGamal params)
+3. `docker/create_active_election.sql` - **Updates** election 1 but lost the ElGamal params
+
+The UPDATE statement in step 3 didn't preserve the ElGamal parameters. They should be:
+
+```sql
+UPDATE elections
+SET
+    is_active = TRUE,
+    start_date = DATE_SUB(NOW(), INTERVAL 1 HOUR),
+    end_date = DATE_ADD(NOW(), INTERVAL 7 DAY),
+    elgamal_p = 23,
+    elgamal_g = 5
+WHERE id = 1;
+```
+
+## After Fix
+
+Once elections have ElGamal keys:
+
+1. Users can register normally
+2. Users can see active elections
+3. Frontend can fetch public keys for voting
+4. Encrypted voting works
+5. Blockchain records votes
+
+## Testing After Fix
+
+```bash
+# 1. Check keys are set
+curl http://localhost:8000/api/votes/public-keys?election_id=1
+
+# 2. Open frontend
+http://localhost:3000
+
+# 3. Register (if needed)
+# 4. Login
+# 5. Click "Participer" on an election
+# 6. Select a candidate
+# 7. Submit vote
+
+# Should see success message with transaction ID
+```
+
+## If Still Not Working
+
+1. Clear browser cache (Ctrl+Shift+Delete)
+2. Restart frontend container: `docker compose restart frontend`
+3. Rebuild frontend if config changed: `docker compose up -d --build frontend`
+4. Check backend logs: `docker compose logs backend | grep -i error`
+5. Check browser console for errors (F12)