feat: Add comprehensive address-first geolocation system for events

This implementation provides automatic geocoding and map integration:

- **Event Model Enhancements:**
  - Automatic geocoding callback using OpenStreetMap Nominatim API
  - 3-tier fallback system: exact coordinates → city-based → country default
  - Fallback coordinates for major French cities (Paris, Lyon, Marseille, etc.)
  - Robust error handling that prevents event creation failures

- **User-Friendly Event Forms:**
  - Address-first approach - users just enter addresses
  - Hidden coordinate fields (auto-generated behind scenes)
  - Real-time geocoding with 1.5s debounce
  - "Ma position" button for current location with reverse geocoding
  - "Prévisualiser" button to show map links
  - Smart feedback system (loading, success, warnings, errors)

- **Enhanced Event Show Page:**
  - Map provider links (OpenStreetMap, Google Maps, Apple Plans)
  - Warning badges when approximate coordinates are used
  - Address-based URLs for better map integration

- **Comprehensive JavaScript Controller:**
  - Debounced auto-geocoding to minimize API calls
  - Multiple geocoding strategies (manual vs automatic)
  - Promise-based geolocation with proper error handling
  - Dynamic map link generation with address + coordinates

- **Failure Handling:**
  - Events never fail to save due to missing coordinates
  - Fallback to city-based coordinates when exact geocoding fails
  - User-friendly warnings when approximate locations are used
  - Maintains existing coordinates on update failures

🤖 Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

app/models/event.rb

@@ -1,5 +1,8 @@
 # Event model representing nightlife events and events
 # Manages event details, location data, and publication state
+require 'net/http'
+require 'json'
+
 class Event < ApplicationRecord
   # Define states for Event lifecycle management
   # draft: Initial state when Event is being created
@@ -19,6 +22,29 @@ class Event < ApplicationRecord
   has_many :tickets, through: :ticket_types
   has_many :orders
 
+  # === Callbacks ===
+  before_validation :geocode_address, if: :venue_address_changed?
+  
+  # === Instance Methods ===
+  
+  # Check if coordinates were successfully geocoded or are fallback coordinates
+  def geocoding_successful?
+    return false if latitude.blank? || longitude.blank?
+    
+    # Check if coordinates are exactly the fallback coordinates
+    fallback_lat = 46.603354
+    fallback_lng = 1.888334
+    
+    !(latitude == fallback_lat && longitude == fallback_lng)
+  end
+  
+  # Get a user-friendly status message about geocoding
+  def geocoding_status_message
+    return nil if geocoding_successful?
+    
+    "Les coordonnées exactes n'ont pas pu être déterminées automatiquement. Une localisation approximative a été utilisée."
+  end
+
   # Validations for Event attributes
   # Basic information
   validates :name, presence: true, length: { minimum: 3, maximum: 100 }
@@ -48,4 +74,102 @@ class Event < ApplicationRecord
 
   # Scope for published events ordered by start time
   scope :upcoming, -> { published.where("start_time >= ?", Time.current).order(start_time: :asc) }
+
+  private
+
+  # Automatically geocode address to get latitude and longitude
+  def geocode_address
+    return if venue_address.blank?
+    
+    # If we already have coordinates and this is an update, try to geocode
+    # If it fails, keep the existing coordinates
+    original_lat = latitude
+    original_lng = longitude
+
+    begin
+      # Use OpenStreetMap Nominatim API for geocoding
+      encoded_address = URI.encode_www_form_component(venue_address.strip)
+      uri = URI("https://nominatim.openstreetmap.org/search?q=#{encoded_address}&format=json&limit=1")
+      
+      response = Net::HTTP.get_response(uri)
+      
+      if response.code == '200'
+        data = JSON.parse(response.body)
+        
+        if data.any?
+          result = data.first
+          self.latitude = result['lat'].to_f.round(6)
+          self.longitude = result['lon'].to_f.round(6)
+          Rails.logger.info "Geocoded address '#{venue_address}' to coordinates: #{latitude}, #{longitude}"
+          return
+        end
+      end
+      
+      # If we reach here, geocoding failed
+      handle_geocoding_failure(original_lat, original_lng)
+      
+    rescue => e
+      Rails.logger.error "Geocoding failed for address '#{venue_address}': #{e.message}"
+      handle_geocoding_failure(original_lat, original_lng)
+    end
+  end
+
+  # Handle geocoding failure with fallback strategies
+  def handle_geocoding_failure(original_lat, original_lng)
+    # Strategy 1: Keep existing coordinates if this is an update
+    if original_lat.present? && original_lng.present?
+      self.latitude = original_lat
+      self.longitude = original_lng
+      Rails.logger.warn "Geocoding failed for '#{venue_address}', keeping existing coordinates: #{latitude}, #{longitude}"
+      return
+    end
+
+    # Strategy 2: Try to extract country/city and use approximate coordinates
+    fallback_coordinates = get_fallback_coordinates_from_address
+    if fallback_coordinates
+      self.latitude = fallback_coordinates[:lat]
+      self.longitude = fallback_coordinates[:lng]
+      Rails.logger.warn "Using fallback coordinates for '#{venue_address}': #{latitude}, #{longitude}"
+      return
+    end
+
+    # Strategy 3: Use default coordinates (center of France) as last resort
+    # This ensures the event can still be created
+    self.latitude = 46.603354  # Center of France
+    self.longitude = 1.888334
+    Rails.logger.warn "Using default coordinates for '#{venue_address}' due to geocoding failure: #{latitude}, #{longitude}"
+  end
+
+  # Extract country/city from address and return approximate coordinates
+  def get_fallback_coordinates_from_address
+    address_lower = venue_address.downcase
+    
+    # Common French cities with approximate coordinates
+    french_cities = {
+      'paris' => { lat: 48.8566, lng: 2.3522 },
+      'lyon' => { lat: 45.7640, lng: 4.8357 },
+      'marseille' => { lat: 43.2965, lng: 5.3698 },
+      'toulouse' => { lat: 43.6047, lng: 1.4442 },
+      'nice' => { lat: 43.7102, lng: 7.2620 },
+      'nantes' => { lat: 47.2184, lng: -1.5536 },
+      'montpellier' => { lat: 43.6110, lng: 3.8767 },
+      'strasbourg' => { lat: 48.5734, lng: 7.7521 },
+      'bordeaux' => { lat: 44.8378, lng: -0.5792 },
+      'lille' => { lat: 50.6292, lng: 3.0573 }
+    }
+    
+    # Check if any known city is mentioned in the address
+    french_cities.each do |city, coords|
+      if address_lower.include?(city)
+        return coords
+      end
+    end
+    
+    # Check for common country indicators
+    if address_lower.include?('france') || address_lower.include?('french')
+      return { lat: 46.603354, lng: 1.888334 } # Center of France
+    end
+    
+    nil
+  end
 end