feat(cli): Implement complete command-line interface

Provides a user-friendly CLI for all GitLab Inbox operations.

src/cli/mod.rs - Clap command definitions:
- Global --config flag for alternate config path
- Subcommands: init, auth-test, doctor, version, backup, reset,
  migrate, sync-status, ingest, list, count, show
- Ingest supports --type (issues/merge_requests), --project filter,
  --force lock override, --full resync
- List supports rich filtering: --state, --author, --assignee,
  --label, --milestone, --since, --due-before, --has-due-date
- List supports --sort (updated/created/iid), --order (asc/desc)
- List supports --open to launch browser, --json for scripting

src/cli/commands/ - Command implementations:

init.rs: Interactive configuration wizard
- Prompts for GitLab URL, token env var, projects to track
- Creates config file and initializes database
- Supports --force overwrite and --non-interactive mode

auth_test.rs: Verify GitLab authentication
- Calls /api/v4/user to validate token
- Displays username and GitLab instance URL

doctor.rs: Environment health check
- Validates config file exists and parses correctly
- Checks database connectivity and migration state
- Verifies GitLab authentication
- Reports token environment variable status
- Supports --json output for CI integration

ingest.rs: Data synchronization from GitLab
- Acquires sync lock with stale detection
- Shows progress bars for issues and discussions
- Reports sync statistics on completion
- Supports --full flag to reset cursors and refetch all data

list.rs: Query local database
- Formatted table output with comfy-table
- Filters build dynamic SQL with parameterized queries
- Username filters normalize @ prefix automatically
- --open flag uses 'open' crate for cross-platform browser launch
- --json outputs array of issue objects

show.rs: Detailed entity view
- Displays issue metadata in structured format
- Shows full description with markdown
- Lists labels, assignees, milestone
- Shows discussion threads with notes

count.rs: Entity statistics
- Counts issues, discussions, or notes
- Supports --type filter for discussions/notes

sync_status.rs: Display sync watermarks
- Shows last sync time per project
- Displays cursor positions for debugging

src/main.rs - Application entry point:
- Initializes tracing subscriber with env-filter
- Parses CLI arguments via clap
- Dispatches to appropriate command handler
- Consistent error formatting for all failure modes

src/lib.rs - Library entry point:
- Exports cli, core, gitlab, ingestion modules
- Re-exports Config, GiError, Result for convenience

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/cli/commands/mod.rs

@@ -0,0 +1,21 @@
+//! CLI command implementations.
+
+pub mod auth_test;
+pub mod count;
+pub mod doctor;
+pub mod ingest;
+pub mod init;
+pub mod list;
+pub mod show;
+pub mod sync_status;
+
+pub use auth_test::run_auth_test;
+pub use count::{print_count, run_count};
+pub use doctor::{print_doctor_results, run_doctor};
+pub use ingest::{print_ingest_summary, run_ingest};
+pub use init::{InitInputs, InitOptions, InitResult, run_init};
+pub use list::{
+    ListFilters, open_issue_in_browser, print_list_issues, print_list_issues_json, run_list_issues,
+};
+pub use show::{print_show_issue, run_show_issue};
+pub use sync_status::{print_sync_status, run_sync_status};