Add Trello Lists support for UI dropdowns

Expose Trello Lists in Board model to enable card creation UI:

- Add List model struct (ID, Name) to types.go
- Add Lists []List field to Board model
- Add GetLists method to TrelloAPI interface
- Refactor private getLists to return []models.List
- Update GetCards to build list map from slice
- Add public GetLists method wrapping private implementation
- Update GetBoardsWithCards to populate Lists field concurrently
- Update mock Trello client in tests to implement GetLists

All tests pass. Boards now include their lists for UI rendering.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

6 files changed, 78 insertions, 28 deletions

diff --git a/SESSION_STATE.md b/SESSION_STATE.md
index 570c987..ce4619e 100644
--- a/SESSION_STATE.md
+++ b/SESSION_STATE.md
@@ -1,24 +1,23 @@
 # Session State
 
-**Current Phase:** Phase 3: Interactivity & Write Operations
-**Current Focus:** Step 1: Trello Write Operations
+## Current Phase
+Phase 3: Interactivity & Write Operations
 
-## Active Issues
-*   `issues/phase3_step1_trello_write.md`: Implementing `CreateCard` and `UpdateCard` in Trello client.
+## Active Task
+Step 2: Trello Lists Support (Backend)
 
-## Completed Issues
-*   `issues/bug_002_tab_state.md`: Fixed tab state persistence.
-*   `issues/bug_001_template_rendering.md`: Fixed template error in notes tab.
+## Recent Completed Tasks
+*   [x] Phase 2.5: Glassmorphism UI (CSS/HTML)
+*   [x] Phase 3 Step 1: Trello Write Ops (Create/Update Card)
 
-## Roadmap
-1.  **Phase 3: Interactivity**
-    *   **Step 1: Trello Write Ops (Active)**
-    *   Step 2: Todoist Write Ops
-    *   Step 3: Unified Quick Add
-2.  **Phase 4: Security Hardening**
-    *   Audit API keys handling.
-    *   Rate limiting.
+## Next Steps
+1.  **Implement Trello Lists Support** (Current)
+    *   Update models and API client to fetch and expose lists.
+2.  **Trello UI Integration**
+    *   Add "Add Card" button and modal.
+    *   Add "Done" checkbox.
+3.  **Todoist Write Ops**
+    *   Implement Create/Complete Task.
 
-## Immediate Next Steps
-1.  Implement `CreateCard` and `UpdateCard` in `internal/api/trello.go`.
-2.  Verify with `internal/api/trello_test.go`.
+## Context
+We are adding write capabilities. We just implemented `CreateCard` and `UpdateCard` in the Trello client. Now we need to expose the Lists so the UI can present a dropdown for "Add Card".
diff --git a/internal/api/interfaces.go b/internal/api/interfaces.go
index 95cc0e7..31da0a8 100644
--- a/internal/api/interfaces.go
+++ b/internal/api/interfaces.go
@@ -19,6 +19,7 @@ type TodoistAPI interface {
 type TrelloAPI interface {
 	GetBoards(ctx context.Context) ([]models.Board, error)
 	GetCards(ctx context.Context, boardID string) ([]models.Card, error)
+	GetLists(ctx context.Context, boardID string) ([]models.List, error)
 	GetBoardsWithCards(ctx context.Context) ([]models.Board, error)
 	CreateCard(ctx context.Context, listID, name, description string, dueDate *time.Time) (*models.Card, error)
 	UpdateCard(ctx context.Context, cardID string, updates map[string]interface{}) error
diff --git a/internal/api/trello.go b/internal/api/trello.go
index 5b87e30..9c18ade 100644
--- a/internal/api/trello.go
+++ b/internal/api/trello.go
@@ -128,9 +128,12 @@ func (c *TrelloClient) GetCards(ctx context.Context, boardID string) ([]models.C
 
 	// Fetch lists to get list names
 	lists, err := c.getLists(ctx, boardID)
-	if err != nil {
-		// If we can't get lists, continue with empty list names
-		lists = make(map[string]string)
+	listMap := make(map[string]string)
+	if err == nil {
+		// Build map of list ID to name
+		for _, list := range lists {
+			listMap[list.ID] = list.Name
+		}
 	}
 
 	// Convert to our model
@@ -140,7 +143,7 @@ func (c *TrelloClient) GetCards(ctx context.Context, boardID string) ([]models.C
 			ID:       apiCard.ID,
 			Name:     apiCard.Name,
 			ListID:   apiCard.IDList,
-			ListName: lists[apiCard.IDList],
+			ListName: listMap[apiCard.IDList],
 			URL:      apiCard.URL,
 		}
 
@@ -158,8 +161,8 @@ func (c *TrelloClient) GetCards(ctx context.Context, boardID string) ([]models.C
 	return cards, nil
 }
 
-// getLists fetches lists for a board and returns a map of list ID to name
-func (c *TrelloClient) getLists(ctx context.Context, boardID string) (map[string]string, error) {
+// getLists fetches lists for a board
+func (c *TrelloClient) getLists(ctx context.Context, boardID string) ([]models.List, error) {
 	url := fmt.Sprintf("%s/boards/%s/lists?key=%s&token=%s", c.baseURL, boardID, c.apiKey, c.token)
 
 	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
@@ -183,15 +186,23 @@ func (c *TrelloClient) getLists(ctx context.Context, boardID string) (map[string
 		return nil, fmt.Errorf("failed to decode response: %w", err)
 	}
 
-	// Convert to map
-	lists := make(map[string]string, len(apiLists))
-	for _, list := range apiLists {
-		lists[list.ID] = list.Name
+	// Convert to model
+	lists := make([]models.List, 0, len(apiLists))
+	for _, apiList := range apiLists {
+		lists = append(lists, models.List{
+			ID:   apiList.ID,
+			Name: apiList.Name,
+		})
 	}
 
 	return lists, nil
 }
 
+// GetLists fetches lists for a specific board
+func (c *TrelloClient) GetLists(ctx context.Context, boardID string) ([]models.List, error) {
+	return c.getLists(ctx, boardID)
+}
+
 // GetBoardsWithCards fetches all boards and their cards in one call
 func (c *TrelloClient) GetBoardsWithCards(ctx context.Context) ([]models.Board, error) {
 	boards, err := c.GetBoards(ctx)
@@ -211,11 +222,18 @@ func (c *TrelloClient) GetBoardsWithCards(ctx context.Context) ([]models.Board,
 			sem <- struct{}{}
 			defer func() { <-sem }()
 
+			// Fetch cards
 			cards, err := c.GetCards(ctx, boards[i].ID)
 			if err == nil {
 				// It is safe to write to specific indices of the slice concurrently
 				boards[i].Cards = cards
 			}
+
+			// Fetch lists
+			lists, err := c.getLists(ctx, boards[i].ID)
+			if err == nil {
+				boards[i].Lists = lists
+			}
 		}(i)
 	}
 
diff --git a/internal/handlers/handlers_test.go b/internal/handlers/handlers_test.go
index 902bebb..13973df 100644
--- a/internal/handlers/handlers_test.go
+++ b/internal/handlers/handlers_test.go
@@ -106,6 +106,10 @@ func (m *mockTrelloClient) GetCards(ctx context.Context, boardID string) ([]mode
 	return []models.Card{}, nil
 }
 
+func (m *mockTrelloClient) GetLists(ctx context.Context, boardID string) ([]models.List, error) {
+	return []models.List{}, nil
+}
+
 func (m *mockTrelloClient) CreateCard(ctx context.Context, listID, name, description string, dueDate *time.Time) (*models.Card, error) {
 	return nil, nil
 }
diff --git a/internal/models/types.go b/internal/models/types.go
index d39a1d6..31308fc 100644
--- a/internal/models/types.go
+++ b/internal/models/types.go
@@ -36,11 +36,18 @@ type Meal struct {
 	RecipeURL  string    `json:"recipe_url"`
 }
 
+// List represents a Trello list
+type List struct {
+	ID   string `json:"id"`
+	Name string `json:"name"`
+}
+
 // Board represents a Trello board
 type Board struct {
 	ID    string `json:"id"`
 	Name  string `json:"name"`
 	Cards []Card `json:"cards"`
+	Lists []List `json:"lists"`
 }
 
 // Card represents a Trello card
diff --git a/issues/phase3_step2_trello_lists.md b/issues/phase3_step2_trello_lists.md
new file mode 100644
index 0000000..f16e226
--- /dev/null
+++ b/issues/phase3_step2_trello_lists.md
@@ -0,0 +1,21 @@
+# Phase 3 Step 2: Trello Lists Support
+
+## Description
+To enable "Add Card" functionality, we need to know the available lists for each board. Currently, the `Board` model does not include lists, and the API client only fetches lists internally to map names.
+
+## Requirements
+1.  **Update Models**: Add `List` struct and `Lists` field to `Board`.
+2.  **Update Interface**: Add `GetLists` to `TrelloAPI`.
+3.  **Update Client**:
+    *   Refactor `getLists` to return `[]models.List`.
+    *   Update `GetBoardsWithCards` to populate `board.Lists`.
+    *   Implement public `GetLists`.
+
+## Plan
+1.  Modify `internal/models/types.go`.
+2.  Modify `internal/api/interfaces.go`.
+3.  Modify `internal/api/trello.go`.
+
+## Verification
+*   Run `go test ./internal/api/...` to ensure no regressions.
+*   (Implicit) The UI will eventually use this data.