feat(dsn): add automatic DSN detection with caching

[betegon]

Summary

Adds GitHub CLI-inspired DSN auto-detection to the Sentry CLI. When users run commands like sentry issue list from a project directory, the CLI now automatically finds the Sentry DSN and resolves org/project without requiring --org and --project flags.

Problem

Users had to manually specify --org and --project flags for every command, or configure defaults. This is tedious, especially when the DSN is already in their project's .env file or source code.

Solution

New DSN detection module that:

1. Detects DSN from multiple sources (in priority order):

   • SENTRY_DSN environment variable
   • .env files (.env.local, .env, .env.development, etc.)
   • JavaScript/TypeScript source code (Sentry.init({ dsn: "..." }))

2. Caches for speed:

   • Fast path (~5ms): verifies cached DSN source file hasn't changed
   • Slow path (~2-5s): full scan on cache miss
   • Stores resolved org/project info to skip API calls

3. Handles conflicts: warns when multiple different DSNs are found

Changes

Area	Description
src/lib/dsn/	New DSN detection module with parser, cache, detector, resolver
src/commands/issue/list.ts	Shows available projects when none specified
src/commands/project/list.ts	Scopes to detected org, shows detection hint
src/types/config.ts	Added dsnCache schema for storing cached entries

Example Output

$ sentry issue list
Issues in my-org/my-project (showing 25):
...
Detected from .env.local

$ sentry project list
SLUG          PLATFORM     NAME
my-project    javascript   My Project
...
Detected from .env.local
Use --org to see projects from other organizations.

Testing

• 20 new tests for DSN detection and caching
• All 94 tests pass