refactor(frontend): unify Tailwind classes — replace hardcoded colors with semantic design tokens

- Replace all bg-blue-600/hover:bg-blue-700 → bg-primary/hover:bg-primary-hover
- Replace all bg-red-600/hover:bg-red-700 → bg-destructive/hover:bg-destructive-hover
- Replace all focus:ring-blue-500 → focus-visible:ring-primary-ring
- Replace all text-blue-600 → text-primary on interactive elements
- Replace all bg-blue-50 → bg-primary-light on UI surfaces
- Replace all bg-red-50 → bg-destructive-light on error surfaces
- Replace all border-blue-200/300 → border-primary-ring
- Replace all border-red-200 → border-destructive-light
- Replace peer-checked:bg-blue-600 → peer-checked:bg-primary (toggles)
- Replace focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-blue-500 patterns
- Keep status badge patterns (bg-*-100 text-*-700) and hover:bg-blue-50 intact

82 files changed, ~400 changes. Build passes.

frontend/src/components/git/CommitModal.svelte

@@ -158,7 +158,7 @@
                             <button
                                 onclick={handleGenerateMessage}
                                 disabled={generatingMessage || loading}
-                                class="text-xs text-blue-600 hover:text-blue-800 disabled:opacity-50 flex items-center"
+                                class="text-xs text-primary hover:text-blue-800 disabled:opacity-50 flex items-center"
                             >
                                 {#if generatingMessage}
                                     <span class="animate-spin mr-1">↻</span> {$t.mapper?.generating}
@@ -169,7 +169,7 @@
                         </div>
                         <textarea
                             bind:value={message}
-                            class="w-full border rounded p-2 h-32 focus:ring-2 focus:ring-blue-500 outline-none resize-none"
+                            class="w-full border rounded p-2 h-32 focus-visible:ring-2 focus-visible:ring-primary-ring outline-none resize-none"
                             placeholder={$t.git?.describe_changes}
                         ></textarea>
                     </div>
@@ -202,7 +202,7 @@
                                 {/each}
                                 {#each status.untracked_files as file}
                                     <li
-                                        class="text-blue-600 flex items-center"
+                                        class="text-primary flex items-center"
                                         title={$t.git?.untracked}
                                     >
                                         <span class="mr-2">?</span>
@@ -258,7 +258,7 @@
                         loading ||
                         (!status?.is_dirty &&
                             status?.staged_files?.length === 0)}
-                    class="px-4 py-2 bg-blue-600 text-white rounded hover:bg-blue-700 disabled:opacity-50"
+                    class="px-4 py-2 bg-primary text-white rounded hover:bg-primary-hover disabled:opacity-50"
                 >
                     {committing ? $t.git?.committing : $t.git?.commit}
                 </button>