feat: install logging, error trapping, PXE/ISO integration tests

Kickstart installs on real hardware failed silently — no error reporting,
only 3 progress callbacks, zero log streaming. This overhaul makes every
install fully observable.

Kickstart improvements:
- Error trapping in %pre and %post (trap ERR sends failure details to bastion)
- 12+ granular progress stages (was 3): SSH, hostname, k3s prep, EFI boot, metadata
- Background log streamer: tails %post output and batch-sends to /api/log
- bastion_log() function for explicit log lines from kickstart scripts

Bastion API:
- POST /api/log — receives raw log lines from kickstart (single or batch)
- InstallLogBuffer — per-MAC ring buffer (2000 lines) + file persistence
- GET /api/logs/:mac — now returns log_lines + log_total alongside stages
- SSE /api/logs/:mac/follow — uses named events (event: stage vs event: log)
- Progress events forwarded to labd via bastion-progress WebSocket message
- Post-provision k3s logs routed through progressBus (was console-only)

dnsmasq fixes found during VM testing:
- HTTP Boot filename: ipxe-real.efi → ipxe.efi (leftover from old 2-stage approach)
- pxe-service directives: only in proxy mode (breaks OVMF PXE in full mode)
- PXEClient vendor class echo for UEFI firmware compatibility

Integration tests:
- PXE boot test: blank UEFI VM → dnsmasq → HTTP Boot → iPXE → bastion → install
- ISO boot test: blank VM boots from bastion-generated ISO → same flow
- Shared helpers: pxe-network (no DHCP, nftables fix), pxe-vm (UEFI + ISO boot)
- test-provision.sh: runs both PXE + ISO tests with prerequisite checks
- 250GB sparse QCOW2 disk (LVM layout needs ~204GB)

201 unit tests passing (11 new).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.taskmaster/templates/example_prd.txt

@@ -0,0 +1,47 @@
+<context>
+# Overview  
+[Provide a high-level overview of your product here. Explain what problem it solves, who it's for, and why it's valuable.]
+
+# Core Features  
+[List and describe the main features of your product. For each feature, include:
+- What it does
+- Why it's important
+- How it works at a high level]
+
+# User Experience  
+[Describe the user journey and experience. Include:
+- User personas
+- Key user flows
+- UI/UX considerations]
+</context>
+<PRD>
+# Technical Architecture  
+[Outline the technical implementation details:
+- System components
+- Data models
+- APIs and integrations
+- Infrastructure requirements]
+
+# Development Roadmap  
+[Break down the development process into phases:
+- MVP requirements
+- Future enhancements
+- Do not think about timelines whatsoever -- all that matters is scope and detailing exactly what needs to be build in each phase so it can later be cut up into tasks]
+
+# Logical Dependency Chain
+[Define the logical order of development:
+- Which features need to be built first (foundation)
+- Getting as quickly as possible to something usable/visible front end that works
+- Properly pacing and scoping each feature so it is atomic but can also be built upon and improved as development approaches]
+
+# Risks and Mitigations  
+[Identify potential risks and how they'll be addressed:
+- Technical challenges
+- Figuring out the MVP that we can build upon
+- Resource constraints]
+
+# Appendix  
+[Include any additional information:
+- Research findings
+- Technical specifications]
+</PRD>