feat: Add application-level settings for CSS color management

- Introduced a new table `application_setting` to store configurable application options.
- Implemented functions to manage CSS color settings, including loading, updating, and reading environment overrides.
- Added a new settings view to render and manage theme colors.
- Updated UI to include a settings page with theme color management and environment overrides display.
- Enhanced CSS styles for the settings page and sidebar navigation.
- Created unit and end-to-end tests for the new settings functionality and CSS management.

scripts/migrations/000_base.sql

@@ -27,6 +27,25 @@ SET name = EXCLUDED.name,
     symbol = EXCLUDED.symbol,
     is_active = EXCLUDED.is_active;
 
+-- Application-level settings table
+CREATE TABLE IF NOT EXISTS application_setting (
+    id SERIAL PRIMARY KEY,
+    key VARCHAR(128) NOT NULL UNIQUE,
+    value TEXT NOT NULL,
+    value_type VARCHAR(32) NOT NULL DEFAULT 'string',
+    category VARCHAR(32) NOT NULL DEFAULT 'general',
+    description TEXT,
+    is_editable BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS ux_application_setting_key
+    ON application_setting (key);
+
+CREATE INDEX IF NOT EXISTS ix_application_setting_category
+    ON application_setting (category);
+
 -- Measurement unit reference table
 CREATE TABLE IF NOT EXISTS measurement_unit (
     id SERIAL PRIMARY KEY,

scripts/migrations/20251025_create_application_setting_table.sql

@@ -0,0 +1,25 @@
+-- Migration: Create application_setting table for configurable application options
+-- Date: 2025-10-25
+-- Description: Introduces persistent storage for application-level settings such as theme colors.
+
+BEGIN;
+
+CREATE TABLE IF NOT EXISTS application_setting (
+    id SERIAL PRIMARY KEY,
+    key VARCHAR(128) NOT NULL UNIQUE,
+    value TEXT NOT NULL,
+    value_type VARCHAR(32) NOT NULL DEFAULT 'string',
+    category VARCHAR(32) NOT NULL DEFAULT 'general',
+    description TEXT,
+    is_editable BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS ux_application_setting_key
+    ON application_setting (key);
+
+CREATE INDEX IF NOT EXISTS ix_application_setting_category
+    ON application_setting (category);
+
+COMMIT;