feat: Implement CodeSnippet functionality with repository and use case layers, update CLI command references

backend/migration/000012_create_codesnippets_table.up.sql

@@ -0,0 +1,40 @@
+-- Create code_snippets table
+CREATE TABLE IF NOT EXISTS code_snippets (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workspace_file_id UUID NOT NULL,
+    -- Basic Info
+    name VARCHAR(255) NOT NULL,
+    snippet_type VARCHAR(255) NOT NULL,
+    language VARCHAR(255) NOT NULL,
+    content TEXT NOT NULL,
+    hash VARCHAR(255) NOT NULL,
+    -- Position Info
+    start_line INTEGER NOT NULL,
+    end_line INTEGER NOT NULL,
+    start_column INTEGER NOT NULL,
+    end_column INTEGER NOT NULL,
+    -- Context Info
+    namespace VARCHAR(255),
+    container_name VARCHAR(255),
+    scope JSONB,
+    dependencies JSONB,
+    -- Structured Info
+    parameters JSONB,
+    signature TEXT,
+    definition_text TEXT,
+    structured_info JSONB,
+    created_at TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
+);
+-- Create indexes for code_snippets table
+-- Hash index for duplicate detection and fast lookup
+CREATE INDEX IF NOT EXISTS codesnippet_hash ON code_snippets (hash);
+-- Workspace file ID index for querying snippets by file
+CREATE INDEX IF NOT EXISTS codesnippet_workspace_file_id ON code_snippets (workspace_file_id);
+-- Language and snippet type index for filtering
+CREATE INDEX IF NOT EXISTS codesnippet_language_type ON code_snippets (language, snippet_type);
+-- Language and name index for searching
+CREATE INDEX IF NOT EXISTS codesnippet_language_name ON code_snippets (language, name);
+-- Add foreign key constraint
+ALTER TABLE code_snippets
+ADD CONSTRAINT fk_codesnippets_workspace_file_id FOREIGN KEY (workspace_file_id) REFERENCES workspace_files(id) ON DELETE CASCADE;