Fix backend deps and apply theme to all Cancel buttons

- Pin bcrypt==3.2.2 to fix passlib bcrypt backend detection error
- Add email-validator==2.2.0 required by Pydantic EmailStr
- Add btn-sm class to Cancel buttons in Admin, Dashboard, Log, Schedule views

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

frontend/src/views/AdminView.vue

@@ -15,7 +15,7 @@
           <input v-model="newChild.name" placeholder="Name" required />
           <input v-model="newChild.color" type="color" title="Color" />
           <button type="submit" class="btn-primary btn-sm">Save</button>
-          <button type="button" @click="showChildForm = false">Cancel</button>
+          <button type="button" class="btn-sm" @click="showChildForm = false">Cancel</button>
         </form>
 
         <div class="item-list">
@@ -46,7 +46,7 @@
           <input v-model="newSubject.icon" placeholder="Icon (emoji)" maxlength="4" style="width:60px" />
           <input v-model="newSubject.color" type="color" title="Color" />
           <button type="submit" class="btn-primary btn-sm">Save</button>
-          <button type="button" @click="showSubjectForm = false">Cancel</button>
+          <button type="button" class="btn-sm" @click="showSubjectForm = false">Cancel</button>
         </form>
 
         <div class="item-list">

frontend/src/views/DashboardView.vue

@@ -77,7 +77,7 @@
             </select>
           </div>
           <div class="dialog-actions">
-            <button @click="showStartDialog = false">Cancel</button>
+            <button class="btn-sm" @click="showStartDialog = false">Cancel</button>
             <button class="btn-primary" @click="startSession">Start</button>
           </div>
         </div>

frontend/src/views/LogView.vue

@@ -43,7 +43,7 @@
             <textarea v-model="newLog.notes" placeholder="What did they do?" rows="3"></textarea>
           </div>
           <div class="form-actions">
-            <button type="button" @click="showForm = false">Cancel</button>
+            <button type="button" class="btn-sm" @click="showForm = false">Cancel</button>
             <button type="submit" class="btn-primary">Save Log</button>
           </div>
         </form>

frontend/src/views/ScheduleView.vue

@@ -23,7 +23,7 @@
             </select>
           </div>
           <div class="form-actions">
-            <button type="button" @click="showCreateForm = false">Cancel</button>
+            <button type="button" class="btn-sm" @click="showCreateForm = false">Cancel</button>
             <button type="submit" class="btn-primary">Create</button>
           </div>
         </form>