feat: unified Claude API key and profile system with z.AI, MiniMax, OpenRouter support (#600)

* feat: add Claude API provider profiles for alternative endpoints

Add support for managing multiple Claude-compatible API endpoints
(z.AI GLM, AWS Bedrock, etc.) through provider profiles in settings.

Features:
- New ClaudeApiProfile type with base URL, API key, model mappings
- Pre-configured z.AI GLM template with correct model names
- Profile selector in Settings > Claude > API Profiles
- Clean switching between profiles and direct Anthropic API
- Immediate persistence to prevent data loss on restart

Profile support added to all execution paths:
- Agent service (chat)
- Ideation service
- Auto-mode service (feature agents, enhancements)
- Simple query service (title generation, descriptions, etc.)
- Backlog planning, commit messages, spec generation
- GitHub issue validation, suggestions

Environment variables set when profile is active:
- ANTHROPIC_BASE_URL, ANTHROPIC_AUTH_TOKEN/API_KEY
- ANTHROPIC_DEFAULT_HAIKU/SONNET/OPUS_MODEL
- API_TIMEOUT_MS, CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC

apps/ui/src/components/layout/sidebar/constants.ts

@@ -1,5 +1,36 @@
 import { darkThemes, lightThemes } from '@/config/theme-options';
 
+/**
+ * Shared constants for theme submenu positioning and layout.
+ * Used across project-context-menu and project-selector-with-options components
+ * to ensure consistent viewport-aware positioning and styling.
+ */
+export const THEME_SUBMENU_CONSTANTS = {
+  /**
+   * Estimated total height of the theme submenu content in pixels.
+   * Includes all theme options, headers, padding, and "Use Global" button.
+   */
+  ESTIMATED_SUBMENU_HEIGHT: 620,
+
+  /**
+   * Padding from viewport edges to prevent submenu overflow.
+   * Applied to both top and bottom edges when calculating available space.
+   */
+  COLLISION_PADDING: 32,
+
+  /**
+   * Vertical offset from context menu top to the "Project Theme" button.
+   * Used for calculating submenu position relative to trigger button.
+   */
+  THEME_BUTTON_OFFSET: 50,
+
+  /**
+   * Height reserved for submenu header area (includes "Use Global" button and separator).
+   * Subtracted from maxHeight to get scrollable content area height.
+   */
+  SUBMENU_HEADER_HEIGHT: 80,
+} as const;
+
 export const PROJECT_DARK_THEMES = darkThemes.map((opt) => ({
   value: opt.value,
   label: opt.label,