feat: add cost/token tracking, monthly budget system, and dry-run mode

- Create PSA_Cost_Tracker class with database table for API call logging
- Log prompt/completion tokens and estimated cost for every OpenRouter API call
- Implement monthly budget system with hard stop (budget of 0 = unlimited)
- Add budget checks in validate_peptide_name() and generate_peptide_content()
- Add dry_run() method to estimate costs before making API calls
- Display monthly usage summary and recent API logs in admin settings
- Add monthly_budget setting to admin interface with number input field
- Update uninstall.php to drop psa_api_logs table on plugin removal

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

.phpcs.xml.dist

@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+<ruleset name="Peptide Search AI">
+	<description>PHP CodeSniffer configuration for Peptide Search AI WordPress plugin</description>
+
+	<!-- Set baseline standard to WordPress-Core -->
+	<rule ref="WordPress-Core">
+		<!-- Allow direct database queries with prepare() statements -->
+		<exclude name="WordPress.DB.DirectDatabaseQuery" />
+	</rule>
+
+	<!-- Files and directories to check -->
+	<file>peptide-search-ai.php</file>
+	<file>includes/</file>
+
+	<!-- Exclude vendor and node_modules -->
+	<exclude-pattern>/vendor/*</exclude-pattern>
+	<exclude-pattern>/node_modules/*</exclude-pattern>
+	<exclude-pattern>/.git/*</exclude-pattern>
+	<exclude-pattern>/.github/*</exclude-pattern>
+
+	<!-- Report settings -->
+	<arg name="colors" />
+	<arg value="sp" />
+	<arg name="report-width" value="120" />
+
+	<!-- Do not fail CI on warnings (only errors should block) -->
+	<config name="ignore_warnings_on_exit" value="1" />
+</ruleset>