Feat/feishu card parsing (#1534)

* feat(feishu): add interactive card message parsing

Add support for parsing inbound Feishu interactive card messages.
When a user sends a card message, the text content is now extracted
and passed to the LLM for processing.

- Add extractCardText() to recursively extract text from card JSON
- Support both JSON 1.0 (legacy) and JSON 2.0 schema formats
- Handle nested elements: header, body, actions, columns
- Extract text from markdown, lark_md, and plain_text elements
- Add comprehensive unit tests for card parsing

Fixes #<issue_number>

💘 Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

* feat(feishu): extract and download images from interactive cards

When receiving interactive card messages, extract embedded images
(img_key, src, icon_key) and download them for LLM processing.

- Add extractCardImageKeys() to recursively extract image keys from card JSON
- Support img elements (img_key, src) and icon elements (icon_key)
- Update downloadInboundMedia() to handle MsgTypeInteractive
- Add comprehensive unit tests for image extraction

Images are downloaded and stored via MediaStore, then appended to
the message content as [image: photo] tags for LLM visibility.

💘 Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

* fix(feishu): simplify card parsing - pass raw JSON, only extract images

Address review feedback: text extraction cannot exhaustively handle all
card formats (i18n_elements, div.fields, etc.). Pass raw JSON to LLM
instead - same approach as MsgTypePost. Only image extraction remains
as images must be downloaded for LLM to process.

- Remove extractCardText() and helper functions
- extractContent() now returns raw JSON for MsgTypeInteractive
- Keep extractCardImageKeys() for downloading embedded images
- Update tests to expect raw JSON for interactive cards

* fix(feishu): don't append media tags to interactive card JSON

Appending media tags like "[attachment]" to raw JSON content produces
invalid JSON format. For interactive cards, the JSON already contains
image information and media refs are downloaded separately.

- Skip appendMediaTags for MsgTypeInteractive to preserve valid JSON
- Add test case for interactive card with images

* fix(feishu): filter out external URLs from card image extraction

Only Feishu-hosted image keys (img_xxx, icon_xxx) can be downloaded via
the Feishu API. External URLs in src field (https://...) should be
filtered out to avoid download failures.

- Add isFeishuImageKey() to detect Feishu-hosted keys vs external URLs
- Update extractImageKeysRecursive to skip external URLs in src field
- Add tests for external URL filtering and mixed scenarios

* feat(feishu): support downloading external images from interactive cards

Previously only Feishu-hosted images (img_key, icon_key) could be
downloaded. Now external URLs in src field are also downloaded via
HTTP and made available to the LLM.

- extractCardImageKeys now returns two slices: Feishu keys and external URLs
- Add downloadExternalImage to download images from HTTP URLs
- Update downloadInboundMedia to handle both Feishu API and HTTP downloads
- Update tests for new function signature

* fix(feishu): use HTTP client with timeout for external image downloads

Replaced http.DefaultClient with a client that has a 30-second timeout
to prevent hanging on unresponsive external URLs.

Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

* fix(feishu): resolve lint errors for shadow and formatting

- Rename err variables to avoid shadowing in downloadExternalImage
- Fix struct field alignment in TestExtractCardImageKeys

Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

* refactor(feishu): pass external image URLs to LLM instead of downloading

Instead of downloading external images from interactive cards, pass
the URLs directly to LLM. This reduces network overhead and lets
vision-capable models fetch images as needed.

- Remove downloadExternalImage function
- Append external URLs to card content for LLM processing
- Only download Feishu-hosted images via API

💘 Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

* fix(feishu): add blank line between functions for gci formatting

* fix(feishu): keep interactive card content as valid JSON

pkg/channels/feishu/common_test.go

@@ -290,3 +290,119 @@ func TestStripMentionPlaceholders(t *testing.T) {
 		})
 	}
 }
+
+func TestExtractCardImageKeys(t *testing.T) {
+	tests := []struct {
+		name             string
+		content          string
+		wantFeishuKeys   []string
+		wantExternalURLs []string
+	}{
+		{
+			name:             "empty content",
+			content:          "",
+			wantFeishuKeys:   nil,
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "invalid JSON",
+			content:          "not json",
+			wantFeishuKeys:   nil,
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "card with no images",
+			content:          `{"schema":"2.0","body":{"elements":[{"tag":"markdown","content":"text"}]}}`,
+			wantFeishuKeys:   nil,
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "single image with img_key",
+			content:          `{"elements":[{"tag":"img","img_key":"img_abc123"}]}`,
+			wantFeishuKeys:   []string{"img_abc123"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "single image with src as Feishu key",
+			content:          `{"elements":[{"tag":"img","src":"img_xyz789"}]}`,
+			wantFeishuKeys:   []string{"img_xyz789"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "multiple images",
+			content:          `{"elements":[{"tag":"img","img_key":"img_1"},{"tag":"div","text":{"content":"text"}},{"tag":"img","img_key":"img_2"}]}`,
+			wantFeishuKeys:   []string{"img_1", "img_2"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "nested image in columns",
+			content:          `{"elements":[{"tag":"div","columns":[{"tag":"img","img_key":"img_col1"},{"tag":"img","img_key":"img_col2"}]}]}`,
+			wantFeishuKeys:   []string{"img_col1", "img_col2"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "image in action",
+			content:          `{"elements":[{"tag":"action","actions":[{"tag":"img","img_key":"img_action"}]}]}`,
+			wantFeishuKeys:   []string{"img_action"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "icon element",
+			content:          `{"elements":[{"tag":"icon","icon_key":"icon_123"}]}`,
+			wantFeishuKeys:   []string{"icon_123"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "complex card with text and images",
+			content:          `{"header":{"title":{"content":"Title"}},"elements":[{"tag":"div","text":{"content":"Description"}},{"tag":"img","img_key":"img_main"}]}`,
+			wantFeishuKeys:   []string{"img_main"},
+			wantExternalURLs: nil,
+		},
+		{
+			name:             "external URL in src",
+			content:          `{"elements":[{"tag":"img","src":"https://example.com/image.png"}]}`,
+			wantFeishuKeys:   nil,
+			wantExternalURLs: []string{"https://example.com/image.png"},
+		},
+		{
+			name:             "mixed Feishu keys and external URLs",
+			content:          `{"elements":[{"tag":"img","img_key":"img_feishu"},{"tag":"img","src":"https://cdn.example.com/external.jpg"},{"tag":"img","src":"img_another"}]}`,
+			wantFeishuKeys:   []string{"img_feishu", "img_another"},
+			wantExternalURLs: []string{"https://cdn.example.com/external.jpg"},
+		},
+		{
+			name:             "multiple external URLs",
+			content:          `{"elements":[{"tag":"img","src":"https://a.com/1.png"},{"tag":"img","src":"http://b.com/2.jpg"}]}`,
+			wantFeishuKeys:   nil,
+			wantExternalURLs: []string{"https://a.com/1.png", "http://b.com/2.jpg"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotFeishuKeys, gotExternalURLs := extractCardImageKeys(tt.content)
+
+			// Compare Feishu keys
+			if len(gotFeishuKeys) != len(tt.wantFeishuKeys) {
+				t.Errorf("extractCardImageKeys() feishuKeys = %v, want %v", gotFeishuKeys, tt.wantFeishuKeys)
+				return
+			}
+			for i, v := range gotFeishuKeys {
+				if v != tt.wantFeishuKeys[i] {
+					t.Errorf("extractCardImageKeys() feishuKeys[%d] = %q, want %q", i, v, tt.wantFeishuKeys[i])
+				}
+			}
+
+			// Compare external URLs
+			if len(gotExternalURLs) != len(tt.wantExternalURLs) {
+				t.Errorf("extractCardImageKeys() externalURLs = %v, want %v", gotExternalURLs, tt.wantExternalURLs)
+				return
+			}
+			for i, v := range gotExternalURLs {
+				if v != tt.wantExternalURLs[i] {
+					t.Errorf("extractCardImageKeys() externalURLs[%d] = %q, want %q", i, v, tt.wantExternalURLs[i])
+				}
+			}
+		})
+	}
+}