[VijinV]

Applications can write logs to files instead of stdout/stderr. The existing editor reads a bounded prefix, which can hide the newest errors. This adds a separate read-only docker.readContainerFileTail endpoint that returns the newest lines in chronological order.

Related: #5703 and the open implementation in #5704. This is an alternative for maintainer review, kept separate from #5194.

• Defaults to 200 lines and 64 KiB; validates positive integer limits up to 5,000 lines and 512 KiB.
• Executes tail with an argument array through Dockerode, applying the byte window before line selection. No shell pipeline or whole-file buffering is used, including on saved SSH servers.
• Returns UTF-8 text with truncated, truncatedByBytes and truncatedByLines metadata. Split leading UTF-8 bytes are skipped; invalid text fails explicitly instead of expanding past the byte cap through replacement characters.
• Checks regular-file metadata before execution; rejects symlinks, FIFOs, devices and directories. Handles missing files/containers, failed reads and unavailable tail utilities explicitly.
• Applies a 10-second caller deadline and bounded stdout/stderr collectors. Preserves docker.read authorization and remote-server organization checks.

Validation: 63 tests pass under Node 24.22.1, including 8 real Linux Docker integration tests for an EOF marker beyond 512 KiB, a 2 MiB line, Unicode, unusual filenames, special-file rejection and missing files. Other tests cover limits, timeouts, output overflow, local/remote clients and actual tRPC authorization. App TypeScript and Biome checks pass. Opt in to integration tests with DOKPLOY_DOCKER_INTEGRATION=1; the suite creates and removes its own temporary container using node:24-alpine.

Limitations: this requires a tail utility and Docker archive metadata access for the selected regular file. The deadline closes caller I/O; Docker exec does not offer a portable way to kill a process blocked by unresponsive storage or a concurrent file replacement. It adds snapshot reads only.