Button consistency sweep + mobile responsiveness patches

- Standardize modal dismiss/cancel buttons to btn-outline-secondary across 70+ views
- Remove btn-sm from page-level Create and Back buttons (Index + Detail pages)
- Fix Edit buttons on Details pages: btn-secondary -> btn-warning
- Fix form Cancel/Back links: btn-secondary -> btn-outline-secondary
- Add 10 CSS patches to site.css for mobile/tablet responsiveness:
  top-navbar overflow prevention, page-header flex-wrap at 575px,
  table action button min-height override, notification dropdown width cap,
  tablet content padding

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Views/Inventory/Details.cshtml

@@ -606,7 +606,7 @@
                 </div>
             </div>
             <div class="modal-footer border-0">
-                <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Close</button>
+                <button type="button" class="btn btn-outline-secondary" data-bs-dismiss="modal">Close</button>
             </div>
         </div>
     </div>
@@ -633,7 +633,7 @@
                 </div>
             </div>
             <div class="modal-footer border-0">
-                <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Close</button>
+                <button type="button" class="btn btn-outline-secondary" data-bs-dismiss="modal">Close</button>
             </div>
         </div>
     </div>

src/PowderCoating.Web/Views/Inventory/Ledger.cshtml

@@ -37,7 +37,7 @@
             </div>
         }
     </div>
-    <a asp-action="Index" class="btn btn-outline-secondary btn-sm">
+    <a asp-action="Index" class="btn btn-outline-secondary">
         <i class="bi bi-arrow-left me-1"></i>Back to Inventory
     </a>
 </div>
@@ -80,7 +80,7 @@
         </div>
         <div class="d-flex gap-2">
             <button type="submit" class="btn btn-primary btn-sm"><i class="bi bi-search"></i></button>
-            <a asp-action="Ledger" class="btn btn-outline-secondary btn-sm">Clear</a>
+            <a asp-action="Ledger" class="btn btn-outline-secondary">Clear</a>
         </div>
     </div>
 </form>