Bump version to 0.1.2; update logging paths and enhance CLI with version command

docs/PRD.md

@@ -68,8 +68,8 @@ The proxy defaults to Opus because this deployment is intended for users whose N
 - The server binds to `127.0.0.1` by default.
 - Default startup reads credentials from user config before environment variables.
 - `--dev` startup reads current-directory `nexus-claude-api.local.json` instead of user config.
-- Default logs are written to `~/.config/nexus-claude-api/logs/nexus-claude-api.log`.
-- `--dev` logs are written to current-directory `logs/nexus-claude-api.log`.
+- Default logs are written to `~/.config/nexus-claude-api/logs/nexus-claude-api-YYYY-MM-DD.log`.
+- `--dev` logs are written to current-directory `logs/nexus-claude-api-YYYY-MM-DD.log`.
 - Missing Nexus credentials fail fast with a clear error.
 - `GET /health` returns healthy status.
 - `GET /v1/models` returns the supported Claude models.

docs/REQUIREMENTS_DESIGN.md

@@ -87,8 +87,8 @@ Config file paths:
 
 Log file paths:
 
-- Default mode: `~/.config/nexus-claude-api/logs/nexus-claude-api.log`
-- Development mode with `--dev`: current-directory `logs/nexus-claude-api.log`
+- Default mode: `~/.config/nexus-claude-api/logs/nexus-claude-api-YYYY-MM-DD.log`
+- Development mode with `--dev`: current-directory `logs/nexus-claude-api-YYYY-MM-DD.log`
 
 When `--claude-code` is used, print a PowerShell command that sets:
 
@@ -248,6 +248,6 @@ CLI tests:
 
 Logging tests:
 
-- Default-mode log path resolves to `~/.config/nexus-claude-api/logs/nexus-claude-api.log`.
-- Development-mode log path resolves to current-directory `logs/nexus-claude-api.log`.
+- Default-mode log path resolves to `~/.config/nexus-claude-api/logs/nexus-claude-api-YYYY-MM-DD.log`.
+- Development-mode log path resolves to current-directory `logs/nexus-claude-api-YYYY-MM-DD.log`.
 - Verbose logging enables debug details without logging secrets.