fix(types): bring real code to zero TypeScript errors, fix three latent bugs

Continues the cleanup from 164 errors down to 88, all of which now sit in
MemStorage — the in-memory dev mock — documented as known debt. Production
server code and the entire client are at zero errors.

Three genuine defects surfaced by the types and fixed:
- deleteAnnouncement returned void while routes check the result and answer
  404 "not found" on falsy: deleting an announcement succeeded in DB but the
  API reported failure on the fallback paths; it now returns a real boolean
- AnnouncementMemoryStorage declared getAnnouncement twice; the first
  implementation was dead at runtime (second definition wins) and is removed
- one route called storage.getDeliveryById(), a method that does not exist,
  crashing with a TypeError whenever hit; it now calls getDelivery()

Everything else is type-level only (annotations, null-to-undefined for
inline styles, honest signatures for markClientCalled's comment parameter
and the invoice verification result's invoiceAmountTTC field), verified
behavior-neutral: client build, production server bundle and the SMTP
end-to-end test all pass unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FHdE9nEh8zHhQNGpCgrtYe

client/src/pages/Groups.tsx

@@ -424,7 +424,7 @@ export default function Groups() {
                       <div className="flex items-center">
                         <div 
                           className="w-10 h-10 flex items-center justify-center mr-3"
-                          style={{ backgroundColor: group.color }}
+                          style={{ backgroundColor: group.color || undefined }}
                         >
                           <Users className="w-5 h-5 text-white" />
                         </div>
@@ -459,7 +459,7 @@ export default function Groups() {
                       <div className="flex items-center">
                         <div 
                           className="w-4 h-4 rounded mr-2"
-                          style={{ backgroundColor: group.color }}
+                          style={{ backgroundColor: group.color || undefined }}
                         />
                         <span className="text-sm text-gray-600">{group.color}</span>
                       </div>
@@ -503,14 +503,7 @@ export default function Groups() {
         setShowCreateModal(false);
         setShowEditModal(false);
         setSelectedGroup(null);
-        setFormData({
-          name: "",
-          color: "#1976D2",
-          nocodbConfigId: "",
-          nocodbTableId: "",
-          nocodbTableName: "",
-          invoiceColumnName: "Ref Facture",
-        });
+        setFormData({ ...EMPTY_GROUP_FORM, invoiceColumnName: "Ref Facture" });
       }}>
         <DialogContent className="sm:max-w-md" aria-describedby="group-modal-description">
           <DialogHeader>