feat(collections): map Outline's named icon set to SF Symbols

Collection.icon can be a literal emoji or a string key into Outline's
own icon library (~50 custom outline-icons keys + ~90 FontAwesome
keys, per shared/utils/IconLibrary.tsx in outline/outline — a
different mapping than the outline-icons package itself, which is
keyed by PascalCase component name, not the string stored on the
collection). Only emoji was handled before, so most non-emoji
collections fell back to a generic folder glyph.

Covers the high-confidence subset with an unambiguous SF Symbol
match; unmapped keys keep falling back to the folder rather than
risk an invalid symbol name rendering blank.

Outpost/Features/Collections/CollectionRowView.swift

@@ -10,6 +10,9 @@ struct CollectionRowView: View {
         } icon: {
             if let emoji = collection.emojiIcon {
                 Text(emoji)
+            } else if let symbolName = collection.icon.flatMap(OutlineIconMapping.sfSymbolName) {
+                Image(systemName: symbolName)
+                    .foregroundStyle(tintColor)
             } else {
                 Image(systemName: "folder.fill")
                     .foregroundStyle(tintColor)
@@ -23,9 +26,9 @@ struct CollectionRowView: View {
 }
 
 private extension OutlineCollection {
-    /// Outline's `icon` field holds either a literal emoji (when a user picked one)
+    /// Outline's `icon` field holds either a literal emoji, or a string key
-    /// or an internal icon-set name (e.g. from their built-in icon picker) — only
+    /// into Outline's own icon set (see OutlineIconMapping) — only the former
-    /// the former is renderable here without a name-to-glyph mapping table.
+    /// is renderable directly, the latter needs the lookup table.
     var emojiIcon: String? {
         // `isEmojiPresentation` misses symbol-class emoji that default to text
         // presentation (e.g. some picked without a variation selector) — `isEmoji`

Outpost/Support/OutlineIconMapping.swift

@@ -0,0 +1,96 @@
+import Foundation
+
+/// Best-effort SF Symbol equivalents for Outline's non-emoji collection icons.
+///
+/// `Collection.icon` is either a literal emoji or a string key into Outline's
+/// own icon set — a mix of custom `outline-icons` components (camelCase keys)
+/// and FontAwesome icons (kebab-case keys, e.g. `faCake` → `"cake"`). The
+/// canonical key list lives in `outline/outline`'s `shared/utils/IconLibrary.tsx`,
+/// not in the `outline-icons` package itself (that's just the raw component
+/// library, keyed by PascalCase component name — a different naming scheme).
+///
+/// SF Symbols has no exact match for everything in that set, so this only
+/// covers keys with a confident, unambiguous equivalent. Anything else falls
+/// back to the generic folder glyph — better than a blank/invalid symbol name
+/// from a wrong guess.
+enum OutlineIconMapping {
+    static func sfSymbolName(for outlineIconKey: String) -> String? {
+        mapping[outlineIconKey]
+    }
+
+    private static let mapping: [String: String] = [
+        // Outline's own custom icon set (camelCase keys).
+        "academicCap": "graduationcap.fill",
+        "bicycle": "bicycle",
+        "beaker": "testtube.2",
+        "buildingBlocks": "cube.fill",
+        "bookmark": "bookmark.fill",
+        "browser": "globe",
+        "collection": "square.grid.2x2.fill",
+        "coins": "dollarsign.circle.fill",
+        "camera": "camera.fill",
+        "carrot": "leaf.fill",
+        "clock": "clock.fill",
+        "cloud": "cloud.fill",
+        "code": "chevron.left.forwardslash.chevron.right",
+        "database": "cylinder.fill",
+        "done": "checkmark.circle.fill",
+        "email": "envelope.fill",
+        "eye": "eye.fill",
+        "feedback": "bubble.left.and.bubble.right.fill",
+        "flame": "flame.fill",
+        "graph": "chart.line.uptrend.xyaxis",
+        "globe": "globe",
+        "hashtag": "number",
+        "info": "info.circle.fill",
+        "image": "photo.fill",
+        "internet": "network",
+        "leaf": "leaf.fill",
+        "library": "books.vertical.fill",
+        "lightbulb": "lightbulb.fill",
+        "lightning": "bolt.fill",
+        "letter": "envelope.fill",
+        "math": "function",
+        "moon": "moon.fill",
+        "notepad": "note.text",
+        "padlock": "lock.fill",
+        "palette": "paintpalette.fill",
+        "pencil": "pencil",
+        "plane": "airplane",
+        "promote": "megaphone.fill",
+        "ramen": "fork.knife",
+        "question": "questionmark.circle.fill",
+        "server": "server.rack",
+        "sun": "sun.max.fill",
+        "shapes": "square.on.circle",
+        "sport": "sportscourt.fill",
+        "smiley": "face.smiling.fill",
+        "target": "target",
+        "team": "person.3.fill",
+        "terminal": "terminal.fill",
+        "thumbsup": "hand.thumbsup.fill",
+        "truck": "shippingbox.fill",
+        "tools": "wrench.and.screwdriver.fill",
+        "vehicle": "car.fill",
+        "warning": "exclamationmark.triangle.fill",
+
+        // FontAwesome icons (kebab-case keys) — high-confidence subset only.
+        "book": "book.fill",
+        "cake": "birthday.cake.fill",
+        "cat": "cat.fill",
+        "dog": "dog.fill",
+        "cube": "cube.fill",
+        "heart": "heart.fill",
+        "gift": "gift.fill",
+        "hammer": "hammer.fill",
+        "laptop": "laptopcomputer",
+        "map": "map.fill",
+        "newspaper": "newspaper.fill",
+        "paw": "pawprint.fill",
+        "shield": "shield.fill",
+        "tree": "tree.fill",
+        "trophy": "trophy.fill",
+        "umbrella": "umbrella.fill",
+        "fish": "fish.fill"
+    ]
+}